Flatteners and Spacing with OAG

[steve2310]

Hi SGL

I am currently having a dilemma with spacing and OAG. After having some problems with a TS-OAG and my Atik EFW2 I decided that it was probably best to go with the especially made ATIK OAG.

However, being that the Atik is 'thicker' than the TS OAG I now have concerns with regard to spacing, in particular with the TV TRF-2008 flattener/reducer that I was hoping to use.

Apparently this FF/R has an optimum spacing of 56mm but looking at the total distance of ccd chip, FW, OAG, this all comes to approximately 64mm (or so I believe).

I'm just wondering how others have overcome this problem? Will this extra distance make the TV FF/R not really useable? Is there any answer to this problem?

Any help or advice would really be appreciated.

Steve.

[BlueAstra]

This is a review of the TV0.8 flattener. It gives the working distance as 56 +/- 4mm. Other flatteners (eg Celestron 0.63: 0.63-105mm, 0.7-50mm, 0.5-225mm) give different magnifications at different working distances implying they will work at other distances. However, the mag will change, and aberration correction may not be optimum. You're fairly close so I guess the best way to find out is to try it.

[steve2310]

Thanks for the link and reply BlueAstra. You are right in the respect that the best thing to do is to just try. Nothing is ever simple is it?

I wonder if anyone else uses a flattener with the ATIK OAG/EFW2/383L set-up?

Thanks again.

[riklaunim]

You may check if you can move the OAG before the flattener if it has nice threads to do so (+/- a filter threaded reducer on the OAG camera to lower it focus point).

[steve2310]

Sorry Rik not sure I understand. Are you saying put the OAG before the focal reducer? If so, not sure that this is possible as the ATIK OAG screws directly onto the FW.

[riklaunim]

If the OAG can be moved that is

Scope -> OAG -> flattener -> wheel -> camera

[steve2310]

Ahhh, ok, the ATIK can't as it is screwed onto the FW. Thanks though. Part of me is starting to wish that I hadn't gone the OAG route. Mmmm, frustrations!

[riklaunim]

Atik OAG just uses big threads and some T-thread adapters. It's not permanently connected to the wheel. So if you want to play with threads - it's doable. I use Brighstar OAG and that one is just T-threaded on both sides (and using OAG is a good thing).

[steve2310]

Thanks Rik. I'll keep faith with it then and have a play with moving the OAG around. I'll have a try connecting the OAG with the EFW2 to begin with and see how round (or not) the stars are towards the edge, and then take it from there.

[gbealnz]

Hate to be the bearer of slightly bad news, but experimentation I have had with my TRF2008 shows a distance of about 50mm is required. This stuffs any use of the TRF2008 and a DSLR, as you don't (normally) have the luxury of adjusting the distance reducer to chip.

I got around this with my SXVR-H16 by using the SX-OAG and a TS filter drawer, and I screwed (and I mean physically screwed) the OAG to the drawer.

Gary

[Psychobilly]

Hate to be the bearer of slightly bad news, but experimentation I have had with my TRF2008 shows a distance of about 50mm is required. This stuffs any use of the TRF2008 and a DSLR, as you don't (normally) have the luxury of adjusting the distance reducer to chip.

I got around this with my SXVR-H16 by using the SX-OAG and a TS filter drawer, and I screwed (and I mean physically screwed) the OAG to the drawer.

Gary

You can now get low profile T adaptors - the standard T-adaptors are designed to give a fixed 55.0mm "register" which is the distance between the the FP (sensor) and the front face of the T adaptor for use with T mount lenses...

Modern Astronomy sell a Canon EOS one...

Peter...

[antimorris]

With the Atik OAG you won't be able to put the OAG on the other side of the flattener/reducer. It does not connect to the filter wheel via t-threads but through 3 small grub screws that go into special holes on the EFW2 so you are kinda set with at least the OAG -> EFW2 -> camera portion unless you make (or have made) a special adapter that will allow you to somehow mount the flattener between the OAG and the EFW2, but with the grub screw attachment side for the OAG it might be a little difficult.