RASA 8 musings

[ollypenrice]

I've just spent what might be the most enjoyable afternoon's processing I can remember. 3.65 hours of OSC on VdB123. It's hardly a 'showcase' object but it's there in the sky, it's interesting and it can be done well or badly. Paul Kummer looked after the capture remotely (for him, but the rig is at my place) and did the stacking. All I did this afternoon was wring the neck out of what was there in the stack and it kept on giving. The camera is an ASI 2600 OSC. At about 1.8 arcsecs per pixel, this is a setup which needs nothing better than a decent EQ6 to give well resolved subs.

We'll post the image later, maybe after a bit of re-framing with a second panel, but the point of this thread is to say that, despite having a dark site and an awful lot of clear nights each year, I am loving the RASA 8/CMOS OSC. You don't quite get Takahashi stars but you can tweak what you do get, and you get many times more photons per pixel.

This rig has rekindled the fire in my imaging heart, and that's at a great site. If I had only limited imaging time the bonus would be considerably multiplied.

I've just checked the RASA price at FLO and, at £2,345.00, it is cheaper than premium apos of comparable focal length and it's harder to set up. However, in combination with CMOS OSC, dual or tri-band filters and StarXterminator for star control, it has (for me) changed the game. Maybe I've just got too old for 20 hours per image?

Olly

[pipnina]

I've given a lot of thought to fast "camera" style scope myself. Though for now I am falling back to your own classical advice point. Which as I recall boiled down to: "Refactors are easy, and this hobby is hard. Make it easier by using a refractor", and I am thus ditching my f4 newtonian which was a source of stress and weight training in favour of a 130 f6.6 apo, to be reduced to at least f4.9. I hope the ease of use and weight reduction is worth it in the face of the slower f speed, but time will tell!

I'd love a RASA, but sadly I'm using a mono cam right now and love my narrowband imaging, so being unable to use an electronic filter wheel hurts! Here in old blighty we still have very poor cloudy weather so betting on having 3 nights to create an SHO image with a RASA using filter drawers sounds risky!

Maybe the solution is just to buy 3 RASAs haha. I think my bank would have some concerns though.

Can't wait to see your result on VDB123! You are one of the best imagers here and have made several pieces I don't think I will ever be able to top in the theoretical 50 years I have left on this sphere!

 

[Clarkey]

6 minutes ago, pipnina said:

theoretical 50 years I have left on this sphere

That's just showing off🤣

But seriously, I am a bit like you. I have tried various options but come to the conclusion the refractors are the simplest option. I am in the process of building a back garden observatory which will house 3 refractors across two mounts and a variety of focal lengths from 910 to 180mm. Given the number of clear nights in Cumbria that should be enough. I have looked at the RASA option and it might still happen one day.  Just need to sell the kids.....😀

[pipnina]

14 minutes ago, Clarkey said:

That's just showing off🤣

But seriously, I am a bit like you. I have tried various options but come to the conclusion the refractors are the simplest option. I am in the process of building a back garden observatory which will house 3 refractors across two mounts and a variety of focal lengths from 910 to 180mm. Given the number of clear nights in Cumbria that should be enough. I have looked at the RASA option and it might still happen one day.  Just need to sell the kids.....😀

Note I say theoretical, I'm sure I can find a way to make diet-induced diabetes, workplace hazards, or something else cut that short haha.

[Stuart1971]

2 hours ago, ollypenrice said:

I've just spent what might be the most enjoyable afternoon's processing I can remember. 3.65 hours of OSC on VdB123. It's hardly a 'showcase' object but it's there in the sky, it's interesting and it can be done well or badly. Paul Kummer looked after the capture remotely (for him, but the rig is at my place) and did the stacking. All I did this afternoon was wring the neck out of what was there in the stack and it kept on giving. The camera is an ASI 2600 OSC. At about 1.8 arcsecs per pixel, this is a setup which needs nothing better than a decent EQ6 to give well resolved subs.

We'll post the image later, maybe after a bit of re-framing with a second panel, but the point of this thread is to say that, despite having a dark site and an awful lot of clear nights each year, I am loving the RASA 8/CMOS OSC. You don't quite get Takahashi stars but you can tweak what you do get, and you get many times more photons per pixel.

This rig has rekindled the fire in my imaging heart, and that's at a great site. If I had only limited imaging time the bonus would be considerably multiplied.

I've just checked the RASA price at FLO and, at £2,345.00, it is cheaper than premium apos of comparable focal length and it's harder to set up. However, in combination with CMOS OSC, dual or tri-band filters and StarXterminator for star control, it has (for me) changed the game. Maybe I've just got too old for 20 hours per image?

Olly

Sounds like you are moving, or at least nudging towards the dark side of CMOS imaging….🤔😀

Edited September 25, 2022 by Stuart1971

[tomato]

I run a big dual refractor rig or a RASA8/SY135 wide field set up under middling skies. I like ‘em both, the RASA/OSC rig especially for it’s ability to deliver decent results in a single night, both with IR/UV or dual band filters.

However, my favourite objects to image are galaxies which tend to be small targets, so if I could only keep one, it would be the refractor rig.

And I will image with the venerable KAF8300 CCDs at some point this season.

Edited September 25, 2022 by tomato
Typo corrected

[Elp]

Always wanted one, I should have bought one back when they were below £2k but I like to keep my rigs small and portable, portable as in all in one bag type of thing. Imaging with a Samyang 135mm at F2.8 equivalent shows on a budget what you can achieve, and the speed is addictive. Add in the aperture of the RASA and I'm sure it's a worthy purchase.

And yes, many hours on the same target does grate.

[ollypenrice]

11 hours ago, pipnina said:

I've given a lot of thought to fast "camera" style scope myself. Though for now I am falling back to your own classical advice point. Which as I recall boiled down to: "Refactors are easy, and this hobby is hard. Make it easier by using a refractor", and I am thus ditching my f4 newtonian which was a source of stress and weight training in favour of a 130 f6.6 apo, to be reduced to at least f4.9. I hope the ease of use and weight reduction is worth it in the face of the slower f speed, but time will tell!

I'd love a RASA, but sadly I'm using a mono cam right now and love my narrowband imaging, so being unable to use an electronic filter wheel hurts! Here in old blighty we still have very poor cloudy weather so betting on having 3 nights to create an SHO image with a RASA using filter drawers sounds risky!

Maybe the solution is just to buy 3 RASAs haha. I think my bank would have some concerns though.

Can't wait to see your result on VDB123! You are one of the best imagers here and have made several pieces I don't think I will ever be able to top in the theoretical 50 years I have left on this sphere!

 

It is certainly true that refractors are the easiest and most reliable optical systems to use and the case for using them is as sound as ever. However, the RASA 8 has changed my view of fast optics. The arrival of StarXterminator is a significant factor in this equation, though. The RASA was tricky to collimate but one 'fast optics' problem which the RASA has overcome is sensitivity to focus. It actually holds focus better than the Tak FSQ106N and a lot better than the later ED FSQs. This came as a real surprise, though Gorann had said the same.

I agree about filters, certainly. And I would not consider for ten seconds the idea of using a RASA in a mobile setup. Call me a coward! The improvement in CMOS OSC over CCD OSC is another important factor in my admiration for the RASA. I don't know why CMOS OSC is so much better but I really think it is, though I haven't done a rigorous back to back comparison.

Technology moves on, sometimes in the right direction. 

Olly

[StuartJPP]

 

12 hours ago, ollypenrice said:

I am loving the RASA 8/CMOS OSC.

Okay, who are you and what have you done with the real Olly?

 

😜

[gorann]

9 minutes ago, StuartJPP said:

 

Okay, who are you and what have you done with the real Olly?

 

😜

Obviously this shows that Olly has a particularly young and open mind, which does not listen to outdated advice from old and grumpy men😄

[CraigT82]

1 minute ago, gorann said:

Obviously this shows that Olly has a particularly young and open mind, which does not listen to outdated advice from old and grumpy men😄

Indeed… it’s nice to hear praise and acceptance of something new rather than the usual “new stuff is rubbish - everything was better in my day” attitude that we see daily for a certain member demographic (not Olly!) 

[tomato]

Olly, compared to two Esprit 150s a RASA8 is definitely in my portable territory. Setting it on the mount here in the Brecon Beacons Autumn AstroCamp was a breeze, the EQ-6 was a different story.😊

Folks, there is a RASA8 on ABS for £1800, I would have gone for it if the COL crisis hadn’t kicked in…

[ollypenrice]

42 minutes ago, tomato said:

Olly, compared to two Esprit 150s a RASA8 is definitely in my portable territory. Setting it on the mount here in the Brecon Beacons Autumn AstroCamp was a breeze, the EQ-6 was a different story.😊

Folks, there is a RASA8 on ABS for £1800, I would have gone for it if the COL crisis hadn’t kicked in…

I'd be too nervous about the physical vulnerability with the camera on, and too nervous about it holding its adjustments if taking the camera on and off. This doesn't mean I have any experience to justify this nervousness and if folks do it, and it works, then better still.

1 hour ago, CraigT82 said:

Indeed… it’s nice to hear praise and acceptance of something new rather than the usual “new stuff is rubbish - everything was better in my day” attitude that we see daily for a certain member demographic (not Olly!) 

I find it interesting that, contrary to what we might expect, astro camera technology has not seen particularly rapid evolution. The CCD cameras available when I started 13 years ago are not very different from those still on sale today. Chips got a bit bigger and pixels a bit smaller but nothing very fundamental changed till CMOS. 

Olly

[tomato]

I too was worried about the scope retaining collimation and how the camera would align when reassembling in the field, so we took all the kit to address this. But as luck would have it, the stars looked as good in the field as when it was in the observatory  back home. Not as convenient as a small refractor for sure, but I was keen to see if I could replicate the results posted on SGL taken at premium sky locations. Got about 90 mins imaging on night one, but alas looks like the next two will be clouded out.

There were concerns about hanging big cameras off the corrector plate, there is a video of a C14 being tested to destruction, it failed with 84 lb on there. It’s not for the faint hearted!