Re: Expected tracking times *Unguided #EXOS2 #TECHNICAL

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
1010 S. 48th Street
Springdale, AR 72762

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
: 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!

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