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As always, many thanks for your advise guys. I did think this was not the easiest of questions to answer definitively!!!!
The easiest first step for me I think is to down adjust the pixel size on my existing set up and see how that changes things, as Jerry suggests (many thanks Jerry), although I'm not sure how that increases the F number? As far as my mount and the existing lens set up goes I'm very happy with the tracking and so on. If adjusting the pixel size doesnt work too well I'll try a higher F number lens first before deciding on the next step.
Thanks again everybody, kind regards, Brian
On Wed, 10 Jul 2019 21:44 Jerry Hubbell - Explore Scientific VP Engineering, <jrh@...
On Wed, Jul 10, 2019 at 10:42 AM, Wes Mcdonald wrote:
You can get a nice little ST 80 scope for 100$. Add $50 for the t adapter and maybe an extension tube and you will be in business at f5. Still sort of wide. Then add a 2x Barlow and you will be at f10 which will fill the fov for many clusters and nebula such as the Swan nebula.
I would caution you that even though the weight limit will support the longer focal length scopes, our general advice for the iEXOS 100 mount is to not exceed 400 mm in focal length because even when guiding the residual PE will be around 2 arc-seconds which limits your plate scale to a minimum of 3-4 arc-seconds/pixel. My general advice when using any DSLR is to lower the resolution (similar to binning on an astro camera) to keep your plate scale around this level.
Modern high megapixel cameras have very small pixels, but when you select from say 16 megapixel to 4 megapixels you double the size of the pixel and you can then increase the focal length without oversampling or having a too small plate scale. This is all based on the limits of the iEXOS 100 mount mechanical performance.
Vice President of Engineering
Explore Scientific, LLC.
jrh at explorescientific.com
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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
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!