Filter Slide for Celestron RASA

[pyrasanth]

A number of people have expressed an interest in to how to mount a camera on the front of the Celestron RASA which incorporates a filter slide.

The filter slide is a part offered by Starizona in the USA for the popular Hyperstar. Since this uses T-threads it can easily be utilized for other imaging platforms. This allows the Hyperstar or other imaging devices to use both 1.25" & 2.00" mounted filters.  These screw into the filter slide holder & additional slides can be purchased making filter change painless. The holder is held firmly with magnets so there is no danger of the filter falling out when the telescope slews.

My Atik camera had to have modified components as the thread is an M54 which needed a modified top for the filter slide & a modified main holder for the RASA as the center hole needed to be wider to cut out vignetting. The main body of the thread for the filter is 2" but adapters are available to convert for 1.25". The components are expensive but very high quality.

The main components are shown below:

The filter slide is as below: You can see the magnets in the middle picture which hold the filter firmly in the holder when fully closed.

The assembled components on the camera look like this

The camera & slide assembly is attached to the RASA front corrector plate. This view shows the Astrodon/Celestron LPR filter which is a 70mm fiilter (very expensive if bought in the UK- over £500.00)

The whole assembly is shown attached to the RASA corrector plate

If you require any more information about this assembly then PM me & I will be happy to help.

[ollypenrice]

Good information. Thanks. I think that it would be better, ideally, to use unmounted filters since these give more clear aperture but, from what we've seen on other threads, you have about 20% vignetting which is not by any means a game stopper.

I suppose my only worry would be that, in exposing filters to the open air, you risk accumulating or changing dust particles so that, ideally, you'd do flats before removing a filter. However, that is a theoretical observation and I'm an imaging pragmatist. Flats taken later will fix the vignetting and any variable dust bunnies, if you get them, can be fixed in Photoshop. I've done a few of those before now!

Olly

[Xplode]

With a scope this fast i doubt there will be any dust bunnies from the filters unless mounted very close to the sensor...maybe if it was dust rabbits instead of dust bunnies it would cause problems?

[harry page]

Hi

Looks very good - who made the adaptors for you ?

I have this on order http://www.teleskop-express.de/shop/product_info.php/info/p7252_TS-M54-Filter-Drawer-for---50mm-and-50-4mm-unmounted-filters.html

will a few weeks till I catch up with you though

Harry

[pyrasanth]

Good information. Thanks. I think that it would be better, ideally, to use unmounted filters since these give more clear aperture but, from what we've seen on other threads, you have about 20% vignetting which is not by any means a game stopper.

I suppose my only worry would be that, in exposing filters to the open air, you risk accumulating or changing dust particles so that, ideally, you'd do flats before removing a filter. However, that is a theoretical observation and I'm an imaging pragmatist. Flats taken later will fix the vignetting and any variable dust bunnies, if you get them, can be fixed in Photoshop. I've done a few of those before now!

Olly

I never see any dust motes to be honest unless they are rock size!- I always give my filters a quick blast on both sides with a photographic blower with the brush removed before placing them back into the filter holder. This works really well. However as the focal length & F ratio becomes slower dust on filters is a problem necessitating greater care with your calibration frames. 

[pyrasanth]

Hi

Looks very good - who made the adaptors for you ?

I have this on order http://www.teleskop-express.de/shop/product_info.php/info/p7252_TS-M54-Filter-Drawer-for---50mm-and-50-4mm-unmounted-filters.html

will a few weeks till I catch up with you though

Harry

The adapters are from Starizona in the USA. I tried a couple of other filter holders which were mostly not very good. The Starizona ones in my opinion are the best but as I said expensive but I definitely believe you get what you pay for.

[Xplode]

Hi

Looks very good - who made the adaptors for you ?

I have this on order http://www.teleskop-express.de/shop/product_info.php/info/p7252_TS-M54-Filter-Drawer-for---50mm-and-50-4mm-unmounted-filters.html

will a few weeks till I catch up with you though

Harry

I'm using the same type for my DSLR, seems pretty good so far