RASA 8 dilemma, advice please

[symmetal]

Having just received my third RASA 8, as the previous two had bad flare issues as described here, the third one is just as bad, or rather worse, despite Celestron having said it had been checked for this issue. FLO have been great in liasing with Celestron and arranging the replacements and after FLO informed them of this third scope having the same problem, Celestron have stopped shipment of RASA 8s and will be returning them all to the factory for correction of this issue as it's more widespread than they originally thought. Celestron say they will collect mine for free and have it sent back to the factory to be fixed, but have no timescale as to when the fixed scopes will be available again. Some on the CN forum have been waiting for a year or so with no proper resolution for this issue.

This third scope is actually worse than the other 2 in that a 180mm mask does not cure the flares over the majority of the frame and that a mask of around 170mm may be needed which is too much I think to lose in the meantime.

Instead of waiting, Celestron, via FLO, have asked if I would like to upgrade to a RASA 11 instead, which they will offer at a discount to help reimberse me for the hassle I've endured so far.

I'm sorely tempted, depending on what the actual discount is, as it has a large imaging circle so along with the ASI2600MC, I can use my ASI6200MM with a filter slide holder if I wanted for proper narrowband imaging. On second thought the Astronomik NB filters likely won't work at f2.2. The backfocus is 55mm and not the 25mm of the RASA 8. Its 650mm focal length, so mosaics may be needed for some targets but at f2.2 they won't take long. 😀  

The drawback is it's 19.5kg tube weight and the AZ-EQ6 I used with the RASA 8 has an imaging limit of 18kg. With accessories this will be at least 22kg I imagine.

This means a new mount also. The Ioptron range seem popular and the CEM70 is a similar price to many of their range, and while the majority have an upper weight limit around 20kg the CEM70 is 31.8kg, It doesn't have the added luxuries like encoders, i-guider or wi-fi, but being used with a standard guide scope and phd2, encoders and i-guider aren't required, and I don't need wi-fi.

There's also the Hem44 harmonic drive mount for a similar price, but weight and size aren't an issue for me as it will be on a permanent pier and the CEM70 looks more robust for an expensive scope. 🙂

Does anybody think it's worth considering the RASA 11 or can you see some disadvantages, rather than waiting for what may be a long time for a working RASA 8. If I get one, is it worth trying it on the AZ-EQ6 first to see how it performs, or should I opt for a better mount at the outset, and do you have any recommendations other than the CEM70 around that price range which should be considered.

Thanks for getting this far anyway and any help offered. 😊

Alan

Edited October 4, 2022 by symmetal

[Stuart1971]

Hello again…

Peronally I would go for the 11” version, for a couple of reasons, how long will you have to wait for the 8” and will it actually ever be sorted properly.., secondly when would you get the chance for an 11” at a good reduced price, and if you do love the 8” there is a good chance that at some point you will want to upgrade….

As for the mount, I would try it, on your current mount, as you have nothing to lose, and as for a new mount, what about the new Trident by JTW friction drive and now in stock at ENS optical for £3400, 75kg load, and again never need to upgrade….

‘I personally have the EQ8 and it’s great, it has a few quirks but easily sorted…👍🏻

[scotty38]

On FLO's site it says to reduce the 31.8Kg by a third for imaging so that takes you down to around 20Kg give or take. It will probably be fine with the RASA 11 BUT if it isn't you'll have no comeback at all.......

[Adam J]

13 hours ago, symmetal said:

Having just received my third RASA 8, as the previous two had bad flare issues as described here, the third one is just as bad, or rather worse, despite Celestron having said it had been checked for this issue. FLO have been great in liasing with Celestron and arranging the replacements and after FLO informed them of this third scope having the same problem, Celestron have stopped shipment of RASA 8s and will be returning them all to the factory for correction of this issue as it's more widespread than they originally thought. Celestron say they will collect mine for free and have it sent back to the factory to be fixed, but have no timescale as to when the fixed scopes will be available again. Some on the CN forum have been waiting for a year or so with no proper resolution for this issue.

This third scope is actually worse than the other 2 in that a 180mm mask does not cure the flares over the majority of the frame and that a mask of around 170mm may be needed which is too much I think to lose in the meantime.

Instead of waiting, Celestron, via FLO, have asked if I would like to upgrade to a RASA 11 instead, which they will offer at a discount to help reimberse me for the hassle I've endured so far.

I'm sorely tempted, depending on what the actual discount is, as it has a large imaging circle so along with the ASI2600MC, I can use my ASI6200MM with a filter slide holder if I wanted for proper narrowband imaging. On second thought the Astronomik NB filters likely won't work at f2.2. The backfocus is 55mm and not the 25mm of the RASA 8. Its 650mm focal length, so mosaics may be needed for some targets but at f2.2 they won't take long. 😀  

The drawback is it's 19.5kg tube weight and the AZ-EQ6 I used with the RASA 8 has an imaging limit of 18kg. With accessories this will be at least 22kg I imagine.

This means a new mount also. The Ioptron range seem popular and the CEM70 is a similar price to many of their range, and while the majority have an upper weight limit around 20kg the CEM70 is 31.8kg, It doesn't have the added luxuries like encoders, i-guider or wi-fi, but being used with a standard guide scope and phd2, encoders and i-guider aren't required, and I don't need wi-fi.

There's also the Hem44 harmonic drive mount for a similar price, but weight and size aren't an issue for me as it will be on a permanent pier and the CEM70 looks more robust for an expensive scope. 🙂

Does anybody think it's worth considering the RASA 11 or can you see some disadvantages, rather than waiting for what may be a long time for a working RASA 8. If I get one, is it worth trying it on the AZ-EQ6 first to see how it performs, or should I opt for a better mount at the outset, and do you have any recommendations other than the CEM70 around that price range which should be considered.

Thanks for getting this far anyway and any help offered. 😊

Alan

Personally I would give up on Celestron after that experience and get myself a Tak Epsilon instead had I that kind of money, despite the smaller aperture you are likely to get a sharper image perticually from the 160ED version which has a very impressive spot diagram indeed. Oh and you can use such luxuries as a filter wheel too. 

F2 is in my opinion just not worth the pain. Epsilon at F3.3 or F2.8 will be much less problematic.  

Personally I dont want my hobby to become a source of stress. But hey maybe you view it in a different way. 

Adam 

 

 

Edited October 4, 2022 by Adam J

[Adam J]

double post

Edited October 4, 2022 by Adam J

[scotty38]

27 minutes ago, Adam J said:

Personally I would give up on Celestron after that experience and get myself a Tak Epsilon instead had I that kind of money, despite the smaller aperture you are likely to get a sharper image perticually from the 160ED version which has a very impressive spot diagram indeed. Oh and you can use such luxuries as a filter wheel too. 

F2 is in my opinion just not worth the pain. Epsilon at F3.3 or F2.8 will be much less problematic.  

Personally I dont want my hobby to become a source of stress. But hey maybe you view it in a different way. 

Adam 

 

 

Another scope I drool over.....

[symmetal]

@Stuart1971  @scotty38 @Adam J

Thanks for the replies. 🙂

Yes, I actually really liked the RASA 8 images apart from the awful flares. The f2 aspect wasn't actually an issue like I thought it might be. As depth of focus is so narrow I thought that it would be a struggle getting good stars over the whole frame and the slightest tilt error would be very evident, but all three scopes gave good round corner stars all over an APS-C sensor. The camera spacing is critical though and a 0.5mm error gives awful results. It needs to be within 0.1mm really and the recommended extra 7.5mm spacing only worked on the second scope. The first scope it needed to be 8.0mm and the third 7.8mm before the stars snap into focus all over. Putting the camera on a tilt test jig beforehand is also a necessity I would think.

Reports on the RASA 11 mentioned that mirror flop can be an issue so focus can change as the scope moves around, and that the mirror locks need to be engaged after focusing which would be a pain with autofocusing kicking in with temperature changes. I think these refer to the earlier RASA 11 as the newer V2 version doesn't have mirror locks by the looks of it, and has improved mirror mechanics to improve stability, so hopefully that wouldn't be a problem.

If it wasn't for the backup of FLO, I would be wary of another Celestron product, but if there was again a problem, I'm sure FLO would take care of it. 😊

Yes, the imaging weight limits aren't stated on the Ioptron products, and the visual weight spec on the AZ-EQ6 is 25kg so the 31.5kg of the CEM70 isn't that great a difference in reality as you say scotty38.

Rather, than fork out for on a new mount right away, if I do opt for the RASA 11, I can put it on the AZ-EQ6, as it's within its viewing limits, to check that it gives good results without noticeable mirror flop etc. on quick 5 sec or so exposures, and if I'm happy with it, I can then get the better mount to suit it. 🙂

The Tak Epsilon looks a great scope Adam, but I'm not a fan really of diffraction spikes, and have always been used to the scope and accessories being in a straight line. 

I'll see what FLO say when they get the RASA 11 offer details from Celestron, and decide from there. Thanks again

Alan

[tooth_dr]

3 hours ago, Adam J said:

Epsilon at F3.3 or F2.8 will be much less problematic

Certainly from my experience, F2.8 is still very much a fussy place to be imaging at.  The Epsilon is very well built thought, but at expense of being heavy. Richard had great success with his ed130 out of the box, but I haven’t seen much from the 160 so I don’t know about it but presumably it’s ok. 

[ollypenrice]

What a shame that this production issue has arisen. Since the RASA 8 certainly can work, it surely can be sorted. But how fast?

The 11 can, potentially, give a wider FOV despite its longer focal length but, of course, it will need a new mount. You all know what I'd recommend! Nothing in astronomy that I've ever owned or used beats the Mesu. I'd love an 11 inch RASA on a Mesu but, alas, it wouldn't fit in the robotic shed it would need to live in.

We must all make our own calls on equipment choice and some subjectivity will come into it. Of the three iOptron mounts which have arrived here, two were dead on arrival and the third was performing badly within less than a year. The last one to arrive had a defective electronic component which iOptron could not replace because they were out of stock, so the owner sent it back for refund. I know this is purely anecdotal but, in my shoes, would you buy an iOptron mount?

Olly

[tomato]

First off, can we assume current RASA11s are free of the flare defect?
If so, and FLO’s first class returns policy is in place, what have you got to lose trying one out on the EQ-6? One session will be enough to tell you if the mount is up to it. On that note, I once purchased a second hand Esprit 150 and was keen to test it out but my Mesu was all packed away awaiting a house move, so I tried it out on an EQ-6. I was pleasantly surprised how well the mount performed with that load on board.

[symmetal]

Thanks @ollypenrice

One thing I wasn't doubting was your recommendation for the Mesu . Your experiences with the iOptron mounts is certainly food for thought though. I've always avoided items that begin with a little i up to now, as it seems it's an excuse just to bump up the price. 😏 CN don't like the CEM70 either it seems.

The JTW Trident does look impressive, but aren't sure what the aftersales service will be like in the long term if things go wrong. 🤔.

Alan

[symmetal]

18 minutes ago, tomato said:

First off, can we assume current RASA11s are free of the flare defect?

That was my first query to FLO but as you say with FLO's guarantee, that isn't a problem to be too worried about. 😀 I haven't seen any CN posts on that issue, just on focus and mirror flop, but hopefully the RASA 11 V2 will have improved that.

Your experience with potentially an overloaded EQ6 is good to hear, so I shouldn't be concerned about using it for testing purposes. 🙂

I was wondering about using it with a Mono camera and filter drawer. Does changing the filters have the potential to introduce dust spots at different places, so requiring flats with after every filter change, or is that not such a problem in real life. ?

Alan

[Elp]

I take flats with every filter change, it doesn't take long. Nothing worse than a whole session of photos being unusable due to unsuitable flats. But it's also because of my process, only one filter drawer so each filter swap won't ensure they'll necessarily be in the same place, and focus is adjusted accordingly too so new flats required.

[gorann]

If the price is good I would be very tempted by the RASA11. Since your third RASA8 also was defect I suspect something has gone wrong with a whole batch of either primary mirrors or corrector plates back there in China. Since you will still be running a wide field scope your EQ6 may be able to handle it as long as you stay around 1" RMS. If not, just put yourself in line for a Mesu😅

PS. I understand that the mirror flip problem was solved by making the v2 of the RASA11

Edited October 4, 2022 by gorann

[gorann]

One ore thing. I have never seen a dust bunny in any of my RASA 8 images. I do try to keep everything clean but I think it mainly has to do with the acute light cone of the f/2 system that takes all bunnies well out of focus unless they are on the sensor, Vignetting is also minimal, so I never use flats (just a bit of Gradient Exterminator now and then). What is your experience @ollypenrice? I expect that the situation will be similar with the RASA11, especially with its 55 mm imaging circle, so even full frame APS may be without much vignetting.

Edited October 4, 2022 by gorann

[symmetal]

48 minutes ago, gorann said:

PS. I understand that the mirror flip problems was solved by making the v2 of the RASA11

Thanks Göran, that's good to know. That was one of my main concerns. 🙂 Also, saying to try the EQ6 anyway is good to hear, though I would say the Mesu is a bit outside what I'd like to spend at the moment. 😁

34 minutes ago, gorann said:

One more thing. I have never seen a dust bunny in any of my RASA 8 images.

Ah!, that's interesting. It's true that with all three RASA 8s I had, the camera has been off and on numerous times, and the filters removed and changed, and the flats I took just showed vignetting and that's all. I just thought I was lucky but maybe that wasn't the case.

@Elp Thanks for your reply, but it looks like I might get away with it in this case. I assume you have a more 'normal' scope. 😊

Alan

 

Edited October 4, 2022 by symmetal

[tomato]

My experience with RASA8 flats is the same, i.e. some vignetting visible but no dust motes.

[ollypenrice]

12 hours ago, gorann said:

One ore thing. I have never seen a dust bunny in any of my RASA 8 images. I do try to keep everything clean but I think it mainly has to do with the acute light cone of the f/2 system that takes all bunnies well out of focus unless they are on the sensor, Vignetting is also minimal, so I never use flats (just a bit of Gradient Exterminator now and then). What is your experience @ollypenrice? I expect that the situation will be similar with the RASA11, especially with its 55 mm imaging circle, so even full frame APS may be without much vignetting.

Exactly like yours, Goran. No dust bunnies, ever, with the RASA. In truth, flats make little difference since everything we get can be dealt with in ABE, though we do use flats. Like you, I think its the F ratio blurring them out, though the system is also very well sealed if using an OSC.

I've had a RASA 11 in my hands and would be very doubtful about an EQ6 for it.

Olly

[pipnina]

1 hour ago, ollypenrice said:

Exactly like yours, Goran. No dust bunnies, ever, with the RASA. In truth, flats make little difference since everything we get can be dealt with in ABE, though we do use flats. Like you, I think its the F ratio blurring them out, though the system is also very well sealed if using an OSC.

I've had a RASA 11 in my hands and would be very doubtful about an EQ6 for it.

Olly

My belt modded HEQ5 can't even really handle my 13kg payload of 200mm f4 newt+guider, so given as (as I understand) the EQ6 isn't supposedly a massive upgrade from there I too would feel very uneasy about loading 22kg onto that mount!

 

Also re: fixing vignetting with Abe/dbe. Every time I have tried to correct for vignetting with those gradient extractions I end up getting ringed banding of some sort. I can't show examples right now being at work but on my newt, DSLR+lens, and phone camera Abe/dbe have always failed to remove vignetting fully despite a fair bit of tinkering. Good flats (easy on DSLR and lens, but never worked well on my newt or phone) were absolutely necessary even in the absence of dust for me.

But those systems all have vignettes of 33% up to 66% so very strong, maybe that plays a part here?

[symmetal]

@ollypenrice @pipnina

The EQ6 is rated up to 25kg visually, with the HEQ5 at only 15kg visually, so the RASA 11 shouldn't be in any danger on the EQ6 just for testing purposes. 🙂  If it's a good one and I'm happy, I will then get a proper mount for it, rather than getting a mount beforehand, and then possibly have to send it back as it's not wanted anymore. 

I'd prefer getting a mount from FLO so if not forking out for a Mesu, and iOptron with it seeming reliability issues, there isn't a big choice left, an EQ8 with its apparent Dec backlash issues, or a Celestron CGX-L. 🤔

Celestron are coming back on Friday with the RASA 11 offer, so will have to wait until then before deciding. 🙂

Alan

[Stuart1971]

32 minutes ago, symmetal said:

@ollypenrice @pipnina

The EQ6 is rated up to 25kg visually, with the HEQ5 at only 15kg visually, so the RASA 11 shouldn't be in any danger on the EQ6 just for testing purposes. 🙂  If it's a good one and I'm happy, I will then get a proper mount for it, rather than getting a mount beforehand, and then possibly have to send it back as it's not wanted anymore. 

I'd prefer getting a mount from FLO so if not forking out for a Mesu, and iOptron with it seeming reliability issues, there isn't a big choice left, an EQ8 with its apparent Dec backlash issues, or a Celestron CGX-L. 🤔

Celestron are coming back on Friday with the RASA 11 offer, so will have to wait until then before deciding. 🙂

Alan

Like,I mentioned before, what about the new JTW trident friction mount, at 75kg payload and £3400…? 🤔
 

https://ensoptical.co.uk/index.php?route=product/product&product_id=14330

Edited October 5, 2022 by Stuart1971

[symmetal]

44 minutes ago, Stuart1971 said:

Like,I mentioned before, what about the new JTW trident friction mount, at 75kg payload and £3400…? 🤔
 

https://ensoptical.co.uk/index.php?route=product/product&product_id=14330

Sorry Stuart, I thought I'd replied in my previous post but it looks like it got cut out while editing by accident.

Yes, it looks a very promising mount for the price, but there is only one independent review available from last month, so until it has an established reputation, I'm reluctant to spend that amount of money. Bit of a chicken and egg situation. 🙂 With the OGEM mount seemingly disappeared and many customers left waiting, not sure if this is actually what the OGEM has morphed into or if it is a separate mount. Not sure what guarantees are offered with it, if there are serious issues after a few months use.

Alan

[gorann]

40 minutes ago, symmetal said:

Sorry Stuart, I thought I'd replied in my previous post but it looks like it got cut out while editing by accident.

Yes, it looks a very promising mount for the price, but there is only one independent review available from last month, so until it has an established reputation, I'm reluctant to spend that amount of money. Bit of a chicken and egg situation. 🙂 With the OGEM mount seemingly disappeared and many customers left waiting, not sure if this is actually what the OGEM has morphed into or if it is a separate mount. Not sure what guarantees are offered with it, if there are serious issues after a few months use.

Alan

I agree, from what I have read that company has for years promised to deliver friction mounts and presented imaginary images looking very much like Mesu mounts, but without delivering any, so better wait. There are threads about it. Hopefully they finally made it but I would wait for someone else to buy one and use it for a while.

Edited October 5, 2022 by gorann

[Stuart1971]

1 hour ago, gorann said:

I agree, from what I have read that company has for years promised to deliver friction mounts and presented imaginary images looking very much like Mesu mounts, but without delivering any, so better wait. There are threads about it. Hopefully they finally made it but I would wait for someone else to buy one and use it for a while.

There are many people who have received them now and are using, yes it’s been a long time in the making, but they have finally delivered on the long awaited promises….

I am not personally interested in what happened 2 years ago, on,y what’s happening now, and it seems very promising…but as you say, I too am waiting a while for more feedback, before i part with £3.5k, but if what I read is true, then it sure will give the Mesu a run for it’s money, literally as it’s half the price…and has a proper PA adjuster, unlike the new Mesu’s…that was a big step backwards IMHO

But only time and good reviews will tell…👍🏻

[gorann]

15 minutes ago, Stuart1971 said:

There are many people who have received them now and are using, yes it’s been a long time in the making, but they have finally delivered on the long awaited promises….

I am not personally interested in what happened 2 years ago, on,y what’s happening now, and it seems very promising…but as you say, I too am waiting a while for more feedback, before i part with £3.5k, but if what I read is true, then it sure will give the Mesu a run for it’s money, literally as it’s half the price…and has a proper PA adjuster, unlike the new Mesu’s…that was a big step backwards IMHO

But only time and good reviews will tell…👍🏻

But it sounded like you tried to talk Alan into being one of the beta testers😉

Edited October 5, 2022 by gorann