dark current noise

alexisgreat wrote:

Astrotripper wrote:

alexisgreat wrote:

I need to get 4/3 attachments to connect it to a telescope though and I want to know if I can use my 1.25" light pollution filters with it without much vignetting. How close to the sensor can one get the filter using telescope attachments? I know the flange distance is 19.25mm but I'm hoping that I can get the sensor to filter distance to about 35mm when using my f/6.3 reducer/corrector and to about 54mm when using my Nexstar 8 at f/10. That would mean no vignetting.

This can be tricky. Your usual T2-MFT adapters are actually quite long. Mine is something like 40mm or so. It was annoying me, because when I had the camera attached to my newtonian telescope with this long adapter, the tube on the side where you attach an eyepiece/camera (sorry, can't remember what it's called in English) was almost entirely inside the telescope tube, partly obstructing the primary mirror. So I made my own, "slim" adapter by combining parts of two completely different adapters. I'll try posting some photos of it later.

Thanks I appreciate it! Is there somewhere in this combo where a 1.25" filter can be threaded? I dont think the usual Celestron parts allow this, part numbers 93625 and 93633-A. Ageena Astro has some that might work though.

This is what someone said to me in the AP forum:

neither of those celestron adapter says in the description they allow for 1.25" filters. the SCT to T thread certainly would not. The 93625 1.25" adapter looks like it has internal threads that are there for stray light baffling, and typically also cut to fit 1.25" filter accessories... but i dont see or read any description that it does... other than there is a similar adapter with a 2x magnifying barlow at the end that clearly threads on... #93640

http://www.celestron.com/browse-shop/astronomy/astroimaging-accessories/t-rings-and-adapters/125-universal-barlow-and-t-adapter

I have something like that, but not Celestron. My Sky-Watcher telescope came with a Barlow lens that looks just like that. It has a T thread and can be connected to a T-Ring, and the barlow lens itself is screwed on using a standard filter thread. So you can replace it with a filter of choice. And even the chrome part of the tube is detachable and can be replaced by one from one of the kit eye-pieces. The big question here is, does this Celestron also use a standard filter thread, or not? I have no idea. Maybe you could ask on an astronomy forum like cloudynights, there's bound to be someone with this particular barlow lens that could confirm or deny.

Can't really comment on those other solutions. I don't even know if it would be better to have the filter further away from the sensor (in which case a threaded nosepiece will work) or closer to it (in which case the low profile male/female T2 adapter with a filter thread should do the job), so can't help you much with this.

But I agree with the advice to not use a diagonal when attaching a camera. You definitely don't want to do that.