Jump to content

RASA - Optical Window v's Filters


Recommended Posts

Folks,

Just working on setup for first efforts with RASA 8 + 2600MC. I've got a slide in filter solution as part of the ASG photon cage. Thinking about the backfocus sensitivity of the RASA I'd like to understand what others are doing when considering imaging with dual narrowband filter v's straight OSC. I'd imagine that with / without filter will need backfocus adjustment

I was  planning to remove the optical window from the RASA as a start (iirc this is Celestron guidance?)  and having either the NB filter or a clear baader focusing filter in place (when I want straight OSC) to try to stabilize the backfocus distance?

Overthinking it?

Cheers

Rob

Link to comment
Share on other sites

I removed the RASA optical window (as recommended by Celestron) and use either a UV/IR cut filter for RGB or a NBZ dual band filter. I don’t use a filter drawer, but screw the filters into a modified RASA adapter. I use both a QHY268 c and a RisingCam IMX571c with the scope so there is a lot of chopping and changing with my set up. Thank goodness for BXT to save me hours of tilt adjustments.

  • Like 1
Link to comment
Share on other sites

Hi Rob, looks like we are on a similar learning curve, I got hold of a RASA 8 a few weeks ago and I'm working to get it set up for the winter season. I'm imaging with OSC (ZWO 183MC Pro) and have fitted a Starizona filter drawer, currently carrying a UV cut filter.  I understand that this gives the correct back focus which seems to be confirmed with my first light image. I do however have what I think is a collimation (possibly tilt)  issue to sort out . Impatiently waiting for the next clear night to start playing around again. It will be good to hear how you get on. 

This was a quick trial 30 x 60s subs then processed in PI. Close up of stars is unprocessed single light sub.

Jim 

 

M31 Final Cropped.jpg

Screenshot 2024-08-24 231746.jpg

Edited by saac
  • Like 2
Link to comment
Share on other sites

I have a RASA 11. Removed the Celestron optical window and use a Baader UFC filter drawer. I might be wrong, but I think the ASI2600MC Pro already has a UV/IR cut protective window fitted?  Certainly my ASI2400MC Pro does. So I just use plain glass with same thickness - in my case IDAS Optical Distance Worker and when shooting narrowband IDAS NBZ.

Link to comment
Share on other sites

Yes, like Robin says there is a UV/IR cut filter in the ASI2600MC. I had not heard of the ASG Photon Cage, so I had to look it up. Very interesting although quite expensive. Its is apparently protruding out a bit into the light path. Please keep us updated how it works and if you get any odd optical effects from it. Have you checked that Baader threaded 2" filters will fit (they are a bit high).

Link to comment
Share on other sites

15 minutes ago, gorann said:

Yes, like Robin says there is a UV/IR cut filter in the ASI2600MC. I had not heard of the ASG Photon Cage, so I had to look it up. Very interesting although quite expensive. Its is apparently protruding out a bit into the light path. Please keep us updated how it works and if you get any odd optical effects from it. Have you checked that Baader threaded 2" filters will fit (they are a bit high).

I have the Octopi device on my RASA 11, which does the same job (Photon Cage came after it). Great for fairly easily sorting out tilt and backfocus issues. It does protrude a little into the light path on the 11, but not much, and no odd effects. Flats do their job fine.

Link to comment
Share on other sites

I only have a single 60s light so far, so inconclusive if the photonCage (PG)  generates any artifacts to be cleaned up. I just checked and happily the baader clear filter happily fits in the PG filter drawer despite its extra depth. Planning to use the fast version of the Antlia dual NB filter.

@saac Jim  - I'm sure we're in for a bit of an adventure 🙂 Happy to share notes as and when the sky clears to gives us something other than water vapour to point at..

  • Like 1
  • Thanks 1
Link to comment
Share on other sites

2 hours ago, Jannerland said:

@saac Jim  - I'm sure we're in for a bit of an adventure 🙂 Happy to share notes as and when the sky clears to gives us something other than water vapour to point at..

Thanks, I think we are in for an interesting ride. I had just taken out my UV filter but I think I should put it back in and only change one thing at a time! I have bought and Orion artificial star to see if I can use it for collimation in the day time. I have my doubt that it will work, but it will be worth a shot.

Jim

 

Link to comment
Share on other sites

  • 3 weeks later...

So just to follow up on my previous and at the risk of hijacking Rob's thread, sorry Rob! Anyway I think I've managed to get a better collimation on my RASA 8 . It's not the quickest of exercises but  I think I'm happy with it now; the weird star artefacts are gone and the auto focuser got a tighter focus and much quicker than before (produced a nice v curve).  So this is a trial image (180 x 60 s) and I left the UV cut filter in together with the RASA's optical window.  There does seem to be mixed reports out there as to what to do . Celestron recommend removing the optical window when using a filter while Starizona suggest leaving it in to achieve the necessary back focus when using their filter draw.  I didn't really pay any attention to framing the image, just wanted to see how the collimation turned out. So for a next step I think I'll try a mosaic on M31 using the ASiAir's mosaic framing routine.  I'm just over the moon that the RASA is now collimated. 

Jim 

 

 

M31 Collimation Test 11 Sep.jpeg

Edited by saac
  • Like 1
Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. By using this site, you agree to our Terms of Use.