Topics

Expected tracking times *Unguided #EXOS2 #TECHNICAL

JB1983
 

Proud to say I became a new owner of a Exos2GT PMC8 as of recent. Opted for it over the AVX  and HEQ 5.   

What I'm wondering is what kind of exposure times I can achieve with this unit. I havent found any good info on this.   I'm going to be using a a skywatcher 150pds and a Nikon D5300.   

I live in northern Alberta,Canada so I'm trying to avoid autoguiding and using a laptop especially in our long cold winters.

If I can pull 60s exposures, Id be a happy camper. Anything more would be a bonus.

Jerry Hubbell - Explore Scientific VP Engineering
 

On Wed, Jun 5, 2019 at 01:35 PM, JB1983 wrote:
What I'm wondering is what kind of exposure times I can achieve with this unit. I havent found any good info on this.   I'm going to be using a a skywatcher 150pds and a Nikon D5300. 
Hi JB,  welcome to the forum and thanks for your purchase. 

As you may know, the EXOS 2 is considered a lower-end mount and as such does not have the un-guided tracking ability needed to do effective imaging at the focal length of your Skywatcher 150P-DS (750 mm) It is generally expected that when doing astrophotography with this mount that you need to auto-guide. The native un-guided PE of the EXOS 2 is around 10-15 arc-seconds RMS. We installed the belt drive system to make sure that the mount tracking is very smooth when auto-guiding with a typical auto-guided PE of about 1 arc-second RMS.

At a focal length of 750 mm the plate scale is probably around 1 arc-second/pixel, so unguided you can expect oblong stars of around 5 arc-seconds with a 60 second exposure at best. If you want fairly round stars un-guided, you should limit your focal length to 200 mm.

I hope this helps you understand and sets your expectations accordingly.
 
Jerry Hubbell
Vice President of Engineering

Explore Scientific, LLC.
jrh at explorescientific.com

www.explorescientificusa.com
1010 S. 48th Street
Springdale, AR 72762
1-866-252-3811

Author: Scientific Astrophotography: How Amateurs Can Generate and Use Professional Imaging Data
             Remote Observatories for Amateur Astronomers: Using High-Powered Telescopes From Home


Mark Slade Remote Observatory (MSRO) IAU MPC W54 Equipment
Wilderness, VA
Mounts
: ES PMC-Eight G11 + Telescope Drive Master (TDM)
Scopes: ES 165 FPL-53 ED APO CF, ES 102 FCD100 ED APO CF
Cameras:  QHY174M-GPS + FW, QHY163C
Misc: 3-inch 0.7x Focal Reducer Field Flattener, Filters: Luminance,
Red, V-band Photometric, Diffuser, 200 lpmm Spectral Grating

Software: MaxIm DL 6, Cartes du Ciel, Astrometrica, AstroImageJ, AutoStakkert!

 

JB,
 
What temperatures do you want to operate at?  I'm targeting a -15C limit, but realistically will probably wimp out at -10C (SW Ontario).  Operating in the cold is its own subject... 
 
I have an EXOS2 PMC8 as well.  My scope's FL is 621mm, not as long as yours.  Funny you should mention the 150PDS, because I've had my eye on those.  I love my refractor, but the 150PDS would give me better scale on galaxies.  I'd like to know how you get along with it.
 
Anyway... you probably didn't get the answer you wanted from Jerry, but he gave you the goods.  On both guided and unguided.  
 
My mount is well-tuned, and at my FL, I can get 30s reliably, unguided.  That's it.  Guided - if you take care with the adjustments - it can be crazy-good.  More minutes than I can make use of in my light-polluted Ontario skies.  See link below for an eyebrow-raiser.  Strictly a test of capability, but fun.  For real imaging in my murky skies, I have to use 60-180s exposures or I'll just get swamped.
 
Did I *want* to guide?  No.  I saw it as a complication rather than a solution.  Having done it for a while, I've flipped and now see it as simplifying my imaging rather than complicating it.  It adds reliability that unguided simply didn't have.
 
I spent a lot of time (too much?) getting down into the weeds on my mount hardware and why it did what it did.  And at one point, Jerry took pains to spell out to me that they optimized the mount for guided, not unguided.  What this means to us is that between the PMC-8, the belt drive, and the guiding software (PHD2 usually), the combination is able to overpower the the mechanical shortcomings of an inexpensive mount and make it punch well above its price point.  I did write up my findings in a tuning doc (link below), so other folks could leverage what I found. As always, YMMV.
 
My answer to laptop-in-the-cold was to get a refurbished lenovo x230 with win7pro.  Still available, and cheap.  They're mil-spec tested, and all you have to do is keep the battery reasonably warm. I'll be making a foam wrapper for mine for this winter.  I have a Talentcell on order, to run everything else, so I should be good for several hours of autonomous ops in the cold this year.  And if at home, I can remote into it from the warmth of the house.
 
If you do decide to guide, at 750mm you probably should take care with your guide camera/guidescope FL choices (link below).  I just changed out my guidescope on Jerry's advice and (if seeing permits), can spend most of a session well under 1.0" RMS.  
 
 
Hope this helps...
 
- Bob
 
Tuning doc link:  https://espmceight.groups.io/g/MOUNTS/files/EXOS2PMC8_TuningNotes_v1.pdf
 
900s image post link: https://espmc-eight.groups.io/g/MAIN/message/2920
 
Guidescope calculator link:  https://astronomy.tools/calculators/guidescope_suitability
 
 
--
Mounts: ES PMC-8 EXOS2
Scopes: SV 102EDT, ZWO 60/280 Guide
Cameras:  Nikon D5300, Altair GPCAM2-IMX224C
Software: ASCOM, CdC, AstroTortilla, BYN Pro, Sharpcap, PHD2
Computer:  Thinkpad x230, Win7Pro/64

Chris Tardif
 

On Wed, Jun 5, 2019 at 06:52 PM, Robert Hoskin wrote:
150PDS
Friends....I have the Celestron XLT 150 which I think is the same OTA as the 150PDS.  IMHO... the focuser on that tube is not up to the task of holding a DSLR setup.  I tried it....not good.  I looked at upgrading the focuser and that cost more than I was willing to pay.  With the camera hanging off the side of the OTA I think you're in trouble.  You also need a coma corrector for imaging on a Newtonian which adds more weight.  

My 2 cents...happy to be corrected.

Chris

 

Chris,
 
Re: 150PDS - I spent a lot of time looking at the SW PDS's, while trying to figure out if I should stick with my refractor or not.  For whatever reason, SW now seems to call them BKP DS's.  
 
Anyway, they do aim those at the AP market, they're just not that common on this side of the pond.  Light cone moved, secondary changed, 2-spd Crayford, F5, etc.  You'll only see passing mention of the PDS's on Cloudynights, but go over to Stargazerslounge (British/EU), and they're all over them.  There's a hundred-and-some-odd-page thread with people waxing poetic about the 130PDS - the 150's little brother.  
 
FWIW...
 
- Bob
 
--
Mounts: ES PMC-8 EXOS2
Scopes: SV 102EDT, ZWO 60/280 Guide
Cameras:  Nikon D5300, Altair GPCAM2-IMX224C
Software: ASCOM, CdC, AstroTortilla, BYN Pro, Sharpcap, PHD2
Computer:  Thinkpad x230, Win7Pro/64

JB1983
 
Edited

Thanks for the information and sorry for the late reply.

So after I read your post I did a little investigating and someone made a good point.  
It doesnt matter what mount you end up buying, your probably going to autoguide.

I really dont want crappy pictures so if autoguiding is something I'm going to do down the road anyways, I'm gonna pull the trigger and go that way.

I'm going to purchase an asi120 or 290 mini and pair it with a 50mm F4 guide scope.  Correct me if I'm wrong but that lands me at a 4:1 imaging you guiding ratio at my 750mm and even lower if I go smaller focal length in the future.

Is the explorestars PC version now ASCOM compatible?  Based on my research I'll be using PHD2 for guiding, backyard Nikon to fire my camera and I'd like like to use the explore stars app for goto for easy of locating objects.

So correct me if I'm wrong but the configuration would be camera to to PC via USB, guide camera to PC via usb then the PC to the pmc 8  is wifi and the ASCOM drivers send the info from the guidescope to the pmc8 module that way?   I've heard the st4 port is still a little unreliable.

Once again I appreciate the help. I actually got a little frustrated and almost sent it back for an EQ6R, but its twice the weight, almost twice the price and I really do like the basis of the Exos and hopefully it future proofs me for a few years until I can afford a larger mount.  

And lucky me, a friend of mind ended giving me a used Asus laptop and it should do the trick for running the programs outdoors without issue.

Harry
 

JB, Have you looked at the ZWO ASIair. It seems to combine many aspects that you want, and retain
wireless compatibility, all in one small box. It does support Nikon DSLR, and you mentioned using a ZWO
guide camera. I have no experience with it myself, but I am seriously considering it when I get to that point.
Excellent review on AstroBackyard.com and YouTube.

Harry

--
Harry
Vero Beach, FL
Scopes: ES AR102,  Meade ETX 90 EC (Deforked)
Mounts: ES iExos 100-PMC Eight, ExploreStars IPAD & Fire HD8,
Oberwerk 5000 Tripod, Binos: Oberwerk 15x70, 8x40

Chris Tardif
 

You are correct on your connections but consider that your PC won’t have access to the Internet if you’re using WIFI for the Explore Stars.  This can be achieved, but you need two networks on your PC and you might have to play with the IP configs.  Not impossible, but tricky. 

 

I don’t use the auto-guide port...if you have PHD working you don’t need it.  Please see Dylan O’Donnell’s video on how to properly deal with the ST4 cable....you can watch the whole thing, but the salient bit is at the 3:19 mark.

 

https://www.youtube.com/watch?v=Mt0luBLaHDw

 

EQ6R...*sigh*....The IEXOS-100 was always a starting point for me to see if I like this hobby....I just started....The EQ6R is on my list and the list is down  to two....little ‘r’ me if you want to take that offline.

 

christardif@...

 

 

 

Sent from Mail for Windows 10

 


From: MAIN@ESPMC-Eight.groups.io <MAIN@ESPMC-Eight.groups.io> on behalf of JB1983 <capnjake83@...>
Sent: Thursday, June 13, 2019 1:11:44 AM
To: MAIN@ESPMC-Eight.groups.io
Subject: Re: [ESPMC-Eight] Expected tracking times *Unguided
 

[Edited Message Follows]

Thanks for the information and sorry for the late reply.

So after I read your post I did a little investigating and someone made a good point.  
It doesnt matter what mount you end up buying, your probably going to autoguide.

I really dont want crappy pictures so if autoguiding is something I'm going to do down the road anyways, I'm gonna pull the trigger and go that way.

I'm going to purchase an asi120 or 290 mini and pair it with a 50mm F4 guide scope.  Correct me if I'm wrong but that lands me at a 4:1 imaging you guiding ratio at my 750mm and even lower if I go smaller focal length in the future.

Is the explorestars PC version now ASCOM compatible?  Based on my research I'll be using PHD2 for guiding, backyard Nikon to fire my camera and I'd like like to use the explore stars app for goto for easy of locating objects.

So correct me if I'm wrong but the configuration would be camera to to PC via USB, guide camera to PC via usb then the PC to the pmc 8  is wifi and the ASCOM drivers send the info from the guidescope to the pmc8 module that way?   I've heard the st4 port is still a little unreliable.

Once again I appreciate the help. I actually got a little frustrated and almost sent it back for an EQ6R, but its twice the weight, almost twice the price and I really do like the basis of the Exos and hopefully it future proofs me for a few years until I can afford a larger mount.  

And lucky me, a friend of mind ended giving me a used Asus laptop and it should do the trick for running the programs outdoors without issue.

JB1983
 

Harry,  I was actually just looking at that unit. Seems a few people are using it now and having great success. Only other way I can think of running 2 wifi connections is maybe a wifi dongle via USB, if that even works.  Very cool piece of equipment for down the road, especially the winter months.

Chris,  good to know I ha my connections proper.  What I couldn't wrap my head around is how PHD2 communicates with the mount if there is no direct cabling from the guide scope to the mount itself, but if I'm not mistaken that's where ascom comes in to play?

Right now I'm trying to figure out my guide scope.  I know the imaging to guiding ratio should be around 1:4  so I've been looking at a 50mm f4 and a 60mm f4.6.  I think the 60mm with its 240mm focal length would probbaly be ideal at 750mm focal length of my scope with brings the ratio down to just a little over 1:3 with the asi120 mini and something like 1:2.99 with the asi290 mini.  Too bad it's a 200 dollar gap between the 2 cameras.  I'd like the 290, but my wallet says its gonna be the 120 lol

Wes Mcdonald
 

JB

If you are going to guide, you will want to use ASCOM and serial -- and if you do that forget about Explorestars.  It is not ASCOM compatible and probably won't be for some time to come.  But believe me, that is not a problem.  You can use Stellarium to visually pick stars, and it is fantastic.  You can load it on your Asus and play with it as a planetarium program and see what I mean.  Then just imagine that all you have to do is click on an object and send your scope to it.  Man.  It's nice.   

As you enter into this journey, please understand getting good astrophotographs is far from simple.  You will have to acquire much skill and knowledge -- about many different aspects of the technology involved -- to achieve great results.  This ain't no point and shoot hobby.  Part and parcel to this is the mount and its peculiarities, all the software and their own quirks, and the workflow necessary to get everything just right.  Not to mention the atmosphere, light pollution, and plain old weather.  These are all things that will come about but in a step by step process, with each new piece of knowledge or skill leading to improved results.  

As to guiding and focal lengths.

The rule of thumb for focal lengths being 4:1 is one of those things that is no better than free advice.  I will give you my understanding of things, which as always is possibly flawed in which case I welcome comment.

The deal is sort of this.  You will in general be able to guide your mount to an accuracy of about .3 or so pixels on your guide camera.  That means the guider will hold the guide star within an area about .3 pixels.  This is useful, but not adequate for understanding.  What we want is to hold the guide star to a position which limits its motion on the imaging camera pixel.  Soooo, we need to understand the relationship between the guider pixel and the imaging pixel size, but in image scale arc seconds) not in pixel size (microns).  

The pixel on an imager covers and angular extent of the sky.  The image scale of a pixel in arc seconds is given by the equation 
        
             Res = (P/F)*206.3

where Res is the arc second pixel scale or resolution, F is the scope focal length, and P is the pixel size in microns.

Your f4 guide scope has a focal length of 200mm.  If the guide camera pixel size is about 3.1 microns this gives you a pixel scale for the guider of about 3.2 arc seconds.  Thus you might expect the mount to guide to about 1 arc second.

Now the imaging camera is attached to a scope with a 750mm focal length.  Assume the camera, DSLR, has a 5.2 micron pixel.  Then the image scale for the DSLR and the 750mm scope is 1.43 arc seconds.  Not bad.  It would seem the guider will guide so as to keep the image within one pixel of the imaging camera. 

Set the Res of the camera =  .3*Res of the guide and solve for the ratio of the F...

           Pi/Fi = .3*Pg/Fg

Where Pi is the pixel size of the imager, Fi is the imager scope focal length, and the g subscript denotes the guider.  I have divided each side by the constant 206.3 factor.  

Then 

               3.3 (Fg/Fi) = Pg/Pi

and we want Pi/Pg to be about one. This happens when Fi/Fg is about 3.3:1.  So that's where 4:1 comes from.  

This is all wonderfullness but reality will set in.  PHD2, the guide camera, and the mount constitute a closed loop control system with its own set of dynamics.  This system is trying to control the position of a spot on the guide camera as the spot position is perturbed by many different effects...wind, refraction, atmospheric seeing, vibration, flexure, mount PA error, mount tracking rate error to name a few.  This is why perfect guiding is impossible. The Dance is to get the things you can manage correct, so that the closed loop system will be able to handle the things you cannot manage.  And like any dance, this takes time to get good at it.

So that is lesson 1.  Why is 4:1 suggested.  Its because things can only operationally track to a certain precision and we need to make that precision work with our imager. 

I started out with a 50mm, f4 guide scope and a guide camera with 5.2 micron pixels.  Didn't work as well as I needed, so I got a 60mm guide scope with a 280mm FL.  Better but I want more performance so I am going to go to smaller pixels in the guider one of these days.  You are starting out with a good guide camera pixel scale it seems so you are on the right track it appears.  If you get an imaging camera with smaller pixels than in the example above where I assumed 5.2 microns, you might find you will want to increase the guider FL.  Also, you may find you will want some more aperture to make more guide stars available.

ASI Air is something I would warn you off of if you are just getting started.  All of the software you need to get up and running is basically free by going the ASCOM route with PHD2, POTH, Stellarium, and BYN.  After you get good at using that, or at least schooled in its use, then consider spending the money.  

One nice thing about going wired to ASCOM is that you can use SkySafari on your iPhone or I think Android to control the mount at the same time you use Stellarium or any other program on the PC.  That is a subject I have posted on a lot, and will do so more in the future as needed. 

You will have to get good a polar aligning the mount.  The iEXOS100 needs a bit of help in that regard.  You can use SharpCap I think with your Nikon to get polar aligned if you can see Polaris.  If not you will need to get good at Drift Aligning or find software that will help you align without Polaris.

Finally, if your Nikon is old enough it will not allow shutter control in Bulb with the USB connection, you need a seperate shutter release cord.  BYN manages it for you but you will have to buy the thing.  It's easy to find out.  Just plug your camera into BYN and try to take a bulb exposure.  BYN will fuss if it cannot do so with the USB. If needed I can write an article about the shutter release cable.

You can test out scope control by Stellarium by using the scope simulator in POTH.  Do this.  It is just tricky enough to set up that you will want to do it when there is daylight and you have coffee, music, AC.  You will need to load a helper program called StellariumScope.  Configure Stellarium according to the instruction in StellariumScope and maybe in Stellarium's instructions.

Finally, put on your to-do list to figure out plate solving.  It will make your life a lot easier when you start trying to image deep space objects.  And you might look into Astro Photography Tool (APT) which integrates everything into one interface, and also integrates with Stellarium.

Regards,
Wes.


--
Wes, Southport NC
PMC-8, ES ED 127, 10" LX200GPS, Astro-Tech 8" Newt, ETX-90
Polemaster, Orion ST-80 and SAG
Electrical Engineer, Retired

Wes Mcdonald
 

JB

PHD2 computes the guide requirements and sends them through ascom to the mount.  This is termed pulse guiding.  The data is sent to the mount via the communication method ASCOM has to the mount.  Please, Please, Please save yourself endless grief and go serial.  It is easy if you get the recommended gear.

Wes.


--
Wes, Southport NC
PMC-8, ES ED 127, 10" LX200GPS, Astro-Tech 8" Newt, ETX-90
Polemaster, Orion ST-80 and SAG
Electrical Engineer, Retired

Darryl Ellis
 

Wes,

That is an outstanding explanation of some very intricate stuff, lol!

I say just get started, and enjoy the journey.  

Now let me go get my calculator and figure out where I messed up.  I might need some help here.

But let me ask the question, how do people with super long focal lengths guide, e.g. c8s, c11s, c14s, and lx200s, with 80mm f4 guidescopes, and get amazing pics I might add.

Darryl
--

DHEllis59, Dover, DE
Astro Tech RC 6 w Pegasus Focus Cube,
Orion Starshoot II Pro Imager,
QHY 5 II Guide Camera and 30mm Guidescope,
Explorer Scientific EXOS GT 2 With PMC Eight Controller,
Orion XT8 with Nexus II DSC via Sky Safari Pro,
Celestron Luminous 31mm, Meade MWA 10mm, and 5mm EPs
Celestron Skymaster 15x70 binoculars,
20/20 or better vision in both eyes due to recent cataract surgery!!!
"The LORD by wisdom founded the earth, By understanding He established the heavens" - Proverbs 3:19

JB1983
 

Thanks so very much for the detailed explanation.  I forgot about ascom being utilized by the serial port.  Just so I'm clear, I need another serial cable like the 2 provided to the dec and RA axis that come with the pmc 8 and go from the serial port on the pmc8 unit to the serial port on the laptop? To be honest I didnt even think they still had serial ports on computers haha

In regards to moving to an object, it sounds like stellarium basically does what I thought I'd be using exlorestars for in that regard, I forgot about explorestars not being ascom compliant.

I'll check and see if my Nikon D5300 is operable by USB through BYN but in sure someone had told me a while back that it is.

Sounds like the larger the guidescope aperture and Lowe the ratio the better.  One of my calculations got me down to 1:2.99 so that may at least be a good starting point.

So my routing would actually look more like this,  guide camera via USB to PC, imaging camera to PC via USB, serial cable from ascom port on pmc8 to serial port on PC.  Then use stellaroun  instead of explorestars to move scope to objects, BYN for camera control, and PHD2 will talk to the mount via ascom.

Another quick question, if I'm using ascom, am I still required to use wifi from pmc8 to PC?

I've heard of POTH hub before but last night night I was looking for info on it and have no idea what it is.  Is there any good documentation out there that can give an overview on what it is and how to use it?

I really appreciate the help.  I know this is going to be a steep learning curve so I'm arming myself to the teeth with the knowledge and programs and then once I ahve my guidescope, I'm going to do some dry runs inside to make sure everything talks to one another and then go outside and try and make things happen.

 

JB,
 
FWIW, I just moved from a 50/200mm F4, to ZWO's 60/280mm F4.6 guidescope.  
My guide camera has 3.75 um pixels.  No plans to change pixel size.
 
I was able, with a decently-adjusted EXOS2 and the 50mm, to float between 1.1 and 0.8 RMS, under good conditions.  Mine is all-cables, no wireless.  I wanted to be able to be consistently sub-1.0 RMS, conditions permitting, and Jerry's advice to me was to go longer.  
 
I did that, and it worked.  But it is a tradeoff.  The good news is that round stars for longer exposures became more dependable.  But.  The price of that was that the increased guiding resolution made PHD2 fussier and (for me, anyway), less set-and-forget, and more drive-according-to-conditions.  Basically, I increased PHD2's ability to chase the seeing and it requires a bit more work to settle it down. But I'm sticking with the ZWO.  :-) 
 
My scope is 621mm FL, vs your 750, and my D5300's pixels are 3.95 um, if you want to plug those into Wes's formulas for comparison.  The D5300 works fine with BYN, just watch the USB cable - it's 'special', and you may need to buy Nikon's in order to get enough length.
  
Hope this helps.  
 
- Bob
 
--
Mounts: ES PMC-8 EXOS2
Scopes: SV 102EDT, ZWO 60/280 Guide
Cameras:  Nikon D5300, Altair GPCAM2-IMX224C
Software: ASCOM, CdC, AstroTortilla, BYN Pro, Sharpcap, PHD2
Computer:  Thinkpad x230, Win7Pro/64

Chris Tardif
 

Yes, PHD communicates through ASCOM and the ExploreStars app and ASCOM control of the mount are mutually exclusive. 

 

I don’t get the guide scope to main scope ratio...I have a 30mm guide scope and a 400 mm lens on the camera...not sure how that is supposed to work.

 

C

 

 

Sent from Mail for Windows 10

 


From: MAIN@ESPMC-Eight.groups.io <MAIN@ESPMC-Eight.groups.io> on behalf of JB1983 <capnjake83@...>
Sent: Thursday, June 13, 2019 11:10:12 AM
To: MAIN@ESPMC-Eight.groups.io
Subject: Re: [ESPMC-Eight] Expected tracking times *Unguided
 
Harry,  I was actually just looking at that unit. Seems a few people are using it now and having great success. Only other way I can think of running 2 wifi connections is maybe a wifi dongle via USB, if that even works.  Very cool piece of equipment for down the road, especially the winter months.

Chris,  good to know I ha my connections proper.  What I couldn't wrap my head around is how PHD2 communicates with the mount if there is no direct cabling from the guide scope to the mount itself, but if I'm not mistaken that's where ascom comes in to play?

Right now I'm trying to figure out my guide scope.  I know the imaging to guiding ratio should be around 1:4  so I've been looking at a 50mm f4 and a 60mm f4.6.  I think the 60mm with its 240mm focal length would probbaly be ideal at 750mm focal length of my scope with brings the ratio down to just a little over 1:3 with the asi120 mini and something like 1:2.99 with the asi290 mini.  Too bad it's a 200 dollar gap between the 2 cameras.  I'd like the 290, but my wallet says its gonna be the 120 lol

JB1983
 

Great info Bob.  If I'm not mistaken I still have the factory USB cable that came with the camera so I should be good in that regards.

I almost pulled the trigger on the 50mm/200mm   may be a good starting point for ease of use compared to one with longer focal length.  I did see a 60mm/230mm  so maybe that's a good half way point as well.

I'm guessing that the longer focal length works better in regards to longer exposures in achieving round stars,  what length of exposure with your 50mm guide scope were you at when you started to notice issues ?

Wes Mcdonald
 

Well I think I got some pretty good guiding with my Meade lx200 at 2500mm FL

I used an 80 mm f5 I believe.  400mm.  Ratio 6:1.  So the answer is....great mount?  Can't say.  I had about .3 pic then too.  I didn't image though.

Not that I would recommend it but good pic with great PA and low periodic error and periodic error correction  don't require much guiding over say a 2 minute exposures.  So that is part of the answer.  Our scopes however have a lot of PE and must be guided especially at high f#.  We have seen some pretty nice iexos photos unguided for two minutes but at high field of view.  Heck with low enough f#s you can get some nice pics In alt Az .

Wes



--
Wes, Southport NC
PMC-8, ES ED 127, 10" LX200GPS, Astro-Tech 8" Newt, ETX-90
Polemaster, Orion ST-80 and SAG
Electrical Engineer, Retired

Wes Mcdonald
 

Chris

It's the focal length ratio.  The 30mm guider has a focal length of what, 150mm?100?.  Your 400 mm lens has a FL of 400.  Ratio about 3.5 to 4.

Wes

--
Wes, Southport NC
PMC-8, ES ED 127, 10" LX200GPS, Astro-Tech 8" Newt, ETX-90
Polemaster, Orion ST-80 and SAG
Electrical Engineer, Retired

Chris Tardif
 

Doh, you’re right.  It’s diameter of 30mm, F4 and 120mm focal length.

 

Sent from Mail for Windows 10

 


From: MAIN@ESPMC-Eight.groups.io <MAIN@ESPMC-Eight.groups.io> on behalf of Wes Mcdonald <wesmcd6@...>
Sent: Thursday, June 13, 2019 2:01:58 PM
To: MAIN@espmc-eight.groups.io
Subject: Re: [ESPMC-Eight] Expected tracking times *Unguided
 
Chris

It's the focal length ratio.  The 30mm guider has a focal length of what, 150mm?100?.  Your 400 mm lens has a FL of 400.  Ratio about 3.5 to 4.

Wes

--
Wes, Southport NC
PMC-8, ES ED 127, 10" LX200GPS, Astro-Tech 8" Newt, ETX-90
Polemaster, Orion ST-80 and SAG
Electrical Engineer, Retired

Chris Tardif
 

I am completely set up using ASCOM and here is how it’s all cabled.  I left Explore Stars behind soon after I got the mount. 

 

I hope this helps.

 

  • Powered USB hub velcro’d to the mount.
  • USB cable from the mount to the USB hub
  • Guide Camera plugged into the USB hub
  • USB Cable from camera to the hub
  • One cable from the USB hub to the PC sitting on the tray.
  • Dew heater not shown, but it plugs into the USB hub as well.
  • My current challenge is to figure out plate-solving, but that’s another thread 😊
  • I then remote control the PC from my couch while my wife watches Hand Maids Tale.

 

I use POTHUB and it behaves as expected. 

    • Install the ASCOM driver for the mount
    • Install ASCOM  (POTHUB lives there)
    • Then you can connect to ASCOM from APT, PHD etc.

 

 

Sent from Mail for Windows 10

 


From: MAIN@ESPMC-Eight.groups.io <MAIN@ESPMC-Eight.groups.io> on behalf of JB1983 <capnjake83@...>
Sent: Thursday, June 13, 2019 12:57:18 PM
To: MAIN@ESPMC-Eight.groups.io
Subject: Re: [ESPMC-Eight] Expected tracking times *Unguided
 
Thanks so very much for the detailed explanation.  I forgot about ascom being utilized by the serial port.  Just so I'm clear, I need another serial cable like the 2 provided to the dec and RA axis that come with the pmc 8 and go from the serial port on the pmc8 unit to the serial port on the laptop? To be honest I didnt even think they still had serial ports on computers haha

In regards to moving to an object, it sounds like stellarium basically does what I thought I'd be using exlorestars for in that regard, I forgot about explorestars not being ascom compliant.

I'll check and see if my Nikon D5300 is operable by USB through BYN but in sure someone had told me a while back that it is.

Sounds like the larger the guidescope aperture and Lowe the ratio the better.  One of my calculations got me down to 1:2.99 so that may at least be a good starting point.

So my routing would actually look more like this,  guide camera via USB to PC, imaging camera to PC via USB, serial cable from ascom port on pmc8 to serial port on PC.  Then use stellaroun  instead of explorestars to move scope to objects, BYN for camera control, and PHD2 will talk to the mount via ascom.

Another quick question, if I'm using ascom, am I still required to use wifi from pmc8 to PC?

I've heard of POTH hub before but last night night I was looking for info on it and have no idea what it is.  Is there any good documentation out there that can give an overview on what it is and how to use it?

I really appreciate the help.  I know this is going to be a steep learning curve so I'm arming myself to the teeth with the knowledge and programs and then once I ahve my guidescope, I'm going to do some dry runs inside to make sure everything talks to one another and then go outside and try and make things happen.