Jump to content

Stargazers Lounge Uses Cookies

Like most websites, SGL uses cookies in order to deliver a secure, personalised service, to provide social media functions and to analyse our traffic. Continued use of SGL indicates your acceptance of our cookie policy.

sgl_imaging_challenge_banner_dslr_mirrorlesss_winners.thumb.jpg.9deb4a8db27e7485a7bb99d98667c94e.jpg

fwm891

Baader UFC and RASA 8 problems

Recommended Posts

Caution: Celstron RASA 8 and Baader UFC filter changer problems.

I’ve just purchased a Celestron RASA 8 from First Light Optics (FLO) which is great, no problems with the RASA 8. My problems came when I wanted to fit a filter changer to the RASA 8 to take advantage of the new (ish) multi narrow band filters available for OSC cameras, specifically in my case an ASI 294MC Pro.

I bought a Baader Universal Filter Changer (UFC) from a fellow StarGazersLounge (SGL) member. The UFC was in pristine condition and from looking at Baader’s specification sheet showing all the adapter plates for the UFC’s base (#24591110) I could initially see no problem in finding the right front and back plates to suit. Wrong.

The problem for RASA 8 users is the shorter back focal distance 25mm from the front of the RASA 8, T threaded mounting plate (29mm from the front of the central lens assembly mounting).

For me to achieve this spacing I had to mount the UFC backwards onto the RASA’s T threaded mounting plate (Baader part number #2459126) would have been fine and kept the UFC facing the right way IF there had been a female mounting plate for the ASI 294MC Pro for the other side.

The UFC came with a #2459130 female mounting plate in to which the 294MC fitted. I now had to fit the UFC to the RASA.

I’ve ended up machining a new mounting plate for the UFC as there are no female T threaded plates. This has allowed me to attain the 25mm spacing required but it’s left me with having to insert filters with the wrong face to the sky (RASA side). I emailed Baader (AKA-David Hinds) to ask if there were other mounting plates or a modified filter drawer so filters could be inserted correctly – no, was the basic reply. So I had to think about how to get round the problem or reversed filters.

Solution (for me) has been to make a modified filter drawer so filters can be inserted the correct way round. Currently in a mock-up state (which fits the UFC base unit) I’m awaiting materials to make the final thing. The photos show the original Baader UFC with the wood mock-up. Differences should be evident but what I’ve basically done is to move the filter mounting plate from one side of the filter drawer to the other.

Final photo shows the plate I've made to attach the UFC to the RASA male T threaded mounting.

F Milsom 2nd November 2019.

Original&mock-up_1.jpg

Original&mock-up_2.jpg

Original&mock-up_3.jpg

Slider_mod.jpg

  • Like 1

Share this post


Link to post
Share on other sites

I was looking into the RASA 8 as a portable setup in the field with my caravan. As far as I know this is a known problem with the UFC due to the small backfocus and looks like you've got a good solution, at least for mounting the filters but I suspect you will still have problems with collimating as you will need to remove the camera to access collimation screws? Removing the camera to collimate will mean you are back to square one most likely.

I saw on Facebook in one of the many groups, that Baader are working on a solution for this due early 2020. From what I can gather is the new product will be a filter changer system with a built in tilt adjuster with adjustments on the side so it can be collimated without the need of removing the camera etc... This would be ideal for the RASA 8"

It sounds like this may be the solution to deal with the 28mm backfocus of the RASA 8". I've got the 2inch Baader high speed filters already for my Hyperstar C11 but this never gets removed from the Observatory for the field, so this new changer could be ideal.

  • Like 1

Share this post


Link to post
Share on other sites
44 minutes ago, ianaiken said:

It sounds like this may be the solution to deal with the 28mm backfocus of the RASA 8". I've got the 2inch Baader high speed filters already for my Hyperstar C11 but this never gets removed from the Observatory for the field, so this new changer could be ideal.

I have a  9.25" Hyperstar and a Baader UFC, using the 70mm diameter Varilock variable spacer to achieve the correct back focus.  You mention that yours is permanently installed in an observatory.  This means that you do not remove it from the corrector plate between sessions?  Very intrigued to know what solution you use for a dust cover / lens cap in that case?

Tony

Share this post


Link to post
Share on other sites
11 minutes ago, AKB said:

Very intrigued to know what solution you use for a dust cover / lens cap in that case?

Tony

Hi Tony, does the Varilock spacer fits between the filter drawer and the camera?

I just leave the dew shield on and throw a t shirt over the end it can be left on for months which also saves me doing flats that frequently. The simple things 🙂

  • Thanks 1

Share this post


Link to post
Share on other sites
3 hours ago, ianaiken said:

does the Varilock spacer fits between the filter drawer and the camera?

It fits directly to the telescope side of the UFC body (see attached image.)

 

3 hours ago, ianaiken said:

I just leave the dew shield on and throw a t shirt over the end it

Oh, er, yes, why not?  I was foolishly looking for a more engineered solution.  I think the real challenge is the dew shield – I have a flexible heated one which, TBH, doesnt' stay very straight or round.  Haven't found a UK supplier of metal ones (although I'd prefer lighter weight... carbon fibre perhaps ???!!!)

Tony

 

1240599648_Image06-11-2019at16_06.thumb.jpg.fc5c6ccaa40ad53a868c27bffbcb1635.jpg

Edited by AKB
added image

Share this post


Link to post
Share on other sites

Mine is flexible too but the t-shirt is lightweight enough it doesn't really move. Can you not run some wood down the inside to give it more support? Or invest in a carbon Fibre or I think you can also get proper remote operated closure fins :)

I found this on the new filter system https://www.baader-planetarium.com/en/blog/rasa-8-extreme-images-michael-jaeger-with-ccd-camera-f2-highspeed-filter/ and its called the Baader FCCT (Filter changer camera tilter). I think this is the solution for the RASA 8" filter situation. I knew I had seen something more than just Facebook.

  • Thanks 1

Share this post


Link to post
Share on other sites

I've knocked-up a new filter tray from a block of Delrin. Photos show (I hope) the differences between the original and the Delrin tray. Straight off the machine so needs some cleaning up. I still have to cut the 48mm thread for the filters and fit a suitable ejector pin and pull handle.

As yet I have no collimation problem straight out of the box. Because the RASA's corrector lens assembly is fixed it doesn't (hasn't) needed collimation. Hyperstar is a different matter as from what I've read is an absolute pain to collimate when it's added and when removed to use the original secondary.

I have an Astrozap metal dew shield for my Edge HD 8 which fits the RASA 8, this has it's own dust cap...

Delrin tray-1.jpg

Delrin tray-2.jpg

  • Like 2

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


  • Recently Browsing   0 members

    No registered users viewing this page.

×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.