6 replies to this topic

[miwitte]

I know there was some serious discussions when the RASA first came out on high speed filters, and I am seriously contemplating it getting a 8"RASA. I would like to re-use my ZWO 1600-MM and Gen 1 36mm ZWO filters which I think are 7nm bandwidth. My concern is not being able to illuminate the sensor uniformly which was the discussion. I need to retain the quality of the data I now obtain with my 80mm Stellarvue without spending a arm and leg on filters. Anyone here using the Gen 1 ZWO filters successfully? My plan is also to get the Starizona filter drawers and 36-48mm adapters.

[bobzeq25]

Can you use them?  Sure.

 

Will they cost you some signal compared to high speed narrowband filters?  Also, sure.  How big an impact will that have?  Who could say?

 

They may vignette a bit, nothing that can't be cured with flats.

 

I replaced my 6nm 1.25 Ha filter with a 2 inch 6nm high speed filter (Astronomik MaxFr) when I got my 2600MM camera.  Seemed a shame to spend the bucks on the camera, the time and effort on data collection and processing, and not optimize the filter.  The time and effort on processing is worth more to me than the few hundred bucks for the best filter.

 

But that's your decision to make.

 

Everything pales before the issue of tilt.  One piece of _strong_ advice.  Do not touch collimation unless you're SURE the problem is not tilt.  That could send you down a very bad road.  The scopes tend to be well collimated, but the camera attachment and sensor are very subject to tilt.  If your stars are bad, that's the first place to look.  Collimation is the big deal on slower scopes, tilt is the big deal on the RASA, it's the first suspect if there's a problem.

 

If you do touch collimation, be sure to record the amount you turn each screw so you can reverse the adjustments if necessary.

Edited by bobzeq25, 19 September 2023 - 05:43 PM.

[drprovi57]

I have both the RASA 8 and RASA 11. I agree with the above observations and suggestions.  I have used the 1600MM with 36mm filters - works well.  Regarding tilt - yes!  Do not mess with collimation—issue will be tilt and proper backfocus.  Tilt and Back focus needs to be within 0.2 mm.. very tight tolerances.  I use both the PhotonCage (see https://www.asgastro...sg-photon-cage/). As well as the Octopi (see https://octopi.space/products).  These are expensive, but they work extremely well.  

 

Hope this helps

Jason

[miwitte]

My plan is to buy a new RASA 8" after wasting ungodly amounts of time with a Edge-HD I could barely get correct. The thought of having to go back and forth between the hyperstar, the .7x reducer and native and collimate made me sell. Fast forward 3 years and I need a solution to speed up light gathering thats reliable session to session as the Edge certainly has mirror movement and we know how critical tilt is.

 

The one thing that always makes me nervous on these and the hyperstar is that the corrector plate is the sole support of a fairly heavy camera that is pulling down. Seems super easy to crack the corrector with a simple bump. Also how much deflection would a large camera have during imaging or meridian flip? Does anyone make something to brace the camera and take load off the corrector during movement? (I have a scope buggy to roll in and out of garage and would like to leave things setup.) 

 

If the RASA is more for a dedicate pier mount VS someone taking it in and out and moving it that would be good information to know.

[miwitte]

Im reading a lot on the RASA and filter drawers etc. Seems with the Starizona and the 2600 you have to remove the camera for filter change? That seems ridiculous and very difficult to manage getting the camera back correctly.

[th3r3ds0x]

The one thing that always makes me nervous on these and the hyperstar is that the corrector plate is the sole support of a fairly heavy camera that is pulling down. Seems super easy to crack the corrector with a simple bump.

I had read that when Celestron developed the rasa they tested how much weight the corrector could handle with weight pulling down on it similarly to what a camera would apply, was over 80# before the corrector failed. They’re quite strong.

[miwitte]

Jason you mentioned both the Photon cage as well as the Octopi which appear to be similar competing products. It appears only the photon cage supports the smaller 78mm ZWO1600MM that i have correct? Also with the 1600mm and 36mm filters what did you use for spacers to fit the Photon cage? Could you share some pictures using that set-up so i know what to expect and how long the exposures?

 

While the price for these tilters is steep the ability to adjust tilt and backspacing easily and not waste many valuable nights is well worth it in my mind.Also the Photon Cage build quality and holding the camera will help with setups that are portable.

 

In my scenario in a Borlte 6-7 zone to reduce the length of time needed for a good SHO image a Hyper-Star or RASA system is the only thing that will fit the bill. The RASA with a very good tilt/backspacing mounting/filter drawer is my future it appears.

 

My last question is on portability of the RASA? I have built a dolly setup with wheels to get the scope and mount into the garage in bad weather. Is the RASA only for pier /permanent setups? Will the tilt/backspace/collimation hold up moving the scope on a dolly? This was the setup with the Edge-HD that was so much effort to go from f/10-f/7-f/2. I've moved on from that and now just want a dedicated f/2 light bucket. At some point a Stellarvue 130mm is in the future for smaller objects but my interest is wide field SHO targets.

 

 

 

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