A place for general chat about Sky at Night Magazine
Mon Mar 12, 2012 3:50 pm
I swear my 8" SCT gives much poorer planatary images than my old 6 inch newtonian. I tried for ages last night to get good view of Mars and all I can manage is an orangy blob. No detail at all. Is it just me, do others use SCT on planets ok. I have a Celestron C8 SGT and it does not matter which planet I look at, it never shows any detail. Maybe I am doing something wrong. When I had my 6" Newtonian, it used to give realy clear images of the planets.
Tue Mar 13, 2012 10:25 pm
You might be right; I've just bought a 66mm Sky Watcher Equinox (refractor) OTA and I'd swear its better than my 5" Celestron Omni SCT!
A few possible explanations: differences in field of view, optical errors (collimation, chromatic aberrations, etc.), mount capabilities, and of course different atmospheric conditions. To eliminate the latter we'd have to use both of our 'scopes side by side for comparative viewing.
My bets are on my mount. The smaller lighter scope is held more rigidly that my bigger SCT and that probably counts for a lot.
Any alternative theories?
Wed Mar 14, 2012 2:34 pm
I have the same SCT as you and I've found when the seeing is good its a great scope and can hold its own against anything else of similiar aperture. Seeing is everything, especially if you're UK based. Attached are a couple of pictures of Mars and Jupiter taken through my SCT under very favourable conditions. I can also confirm that visually both these planets did not look too far off these photos at the time (obviously an imaging camera will tease out some extra detail once you have processed your pictures)
SCT's are very good for astro photography. However some Newtonians and refractors can perform a little better when it comes to visual observing. Having said that, with a 3x barlow in mine visually Mars, Saturn and Jupiter look absolutely stunning. But only when the seeing is good. Recently we've had the jet stream going over England so conditions have been pretty poor for observing. But keep at it.
Sky at Night Magazine
- 11-10-20 02-36-00.jpg (50.48 KiB) Viewed 35296 times
- 26-02-2012 23-10-34 F30.jpg (26.33 KiB) Viewed 35296 times
Wed Mar 14, 2012 4:44 pm
Steve thanks very much for that, it gives me hope. So you reckon it is just that the seeing is poor at the moment? I'll keep at it, do you recommend the 3 times barlow is best for this, any particular one you use that you think is worth looking at ?
Wed Mar 14, 2012 5:26 pm
I'd recommend starting with a 2x Barlow. You need very good seeing for imaging with a 3x with the C8 SGT. I've only managed good imaging with it a couple of times. However if you're only observing visually the 3x will serve you well, as long as you're well polar aligned, because you're looking at a very tiny area of the sky.
The seeing is definitely not good right now. But if you are able to get up early then the early hours of the morning on a clear night are usually when you can expect it to be at its best. The Jupiter image was taken at 2.30 am! Though from about 4am is often quite a good time. Provided there's not much wind about.
Good luck and trust me, don't give up on your C8 yet.
Wed Mar 14, 2012 10:35 pm
those are super images! I'm definitely going for a bigger mount and a bigger OTA now!
Thu Mar 15, 2012 10:04 am
8 inch Schmidt Cassegrain scopes are really good for lunar work aswell. Check out my thread in the imaging section to see some recent mosaics: 3-close-up-lunar-mosaics-t126849.html
Mon Jun 17, 2013 12:14 am
The best thing that I ever did to improve the seeing from my C8 was to go out and buy Bob's Knob's. these replace the collomation screws in the C8 and allow you to collomate with ease. Once I did this I found I had twice the telescope. The collomation is point at a bright object like a star or a distant light. Make it out of focus until you see concentric circles. If the scope is out of collomation the circles will not be concentric. Adjust the knobs until the circles are concentric and the star will appear much sharper when the focus is adjusted.
Good luck with the scope.
Powered by phpBB © phpBB Group.
phpBB Mobile / SEO by Artodia.