Icesheet

14 hours ago, GalaxyGael said:

Well, if nebulae and dust regions in wide to medium field are of interest, signal is key, and the case in particular for osc. 

Tak epsilons are among the easiest newts to collimate IMO and like Rasa, retain collimation long term. They are also almost impervious to temperature focus drift. My experience is with the steel tube epsilons, remarkable flat line hfr values all night long.

Any scope at f6 will reduce with 0.8x flattener to f4.8, whether 90mm f6 or the wide range of excellent 80mm f6 scopes.

Your fra400 can also be reduced to f3.9, just under 300 mm focal length and corrects out to aps c sensor size. Fast and wide, big chunky of sky. And it is smaller than the Rasa, so consider whether you lug it in and out for sessions, if that's matters to you. Unless the fov is a concern, can't see much better options than a reduced fra400 you already have really, apart from the f3.9 fsq85 with new reducer, but it's a big outlay for something very similar.

The TS 110flat f/4.8 is big and expensive, but slower than a reducer on your fra400, which might be the best option to see if wide field and speed is something that gives you the improvement you are testing the waters for?

The new reducer does t fix the aperture vignetting of inverse lighthouse beams on fsq85, nothing can formally as it's part and parcel of the optical design. It just shows more when reduced with modern sensors, but mitigated for narrow bandpass (3-5nm) NB imaging. The new 3 or 5 nm dual band filters might be good there if the star shapes matter, personal taste.

Ah, ok. Misunderstood you. I thought you meant there were native flat field f4.8 scopes. That TS110 looks interesting though if it corrects as well as it says. No, the reducer on the FRA doesn’t interest me. Although the stars are round, it bloats them even further so I’ll likely get an even softer image. I get this should be less of an issue than longer focal length galaxy type imaging but I see it and it bugs me 😆 So, if I’m staying refractor I would like something that has tighter, sharper stars. 
 

I think, I’m just about settled that a fast reflector is what will give me the results I want. Weight is a consideration for sure and I think the RASA is the upper limit. Worst case is two trips out but it’s literally just outside my door so should be fine. 

2 hours ago, ollypenrice said:

Today a new dataset fell into my lap, Paul having captured 116x3 minutes on little Sh2-257, mostly to enhance our Orion-Monoceros widefield. It gave me a chance to study RASA resolution rather nicely, though. Here's the full field just given a basic stretch.

Now let's have a look at the Sharpless object itself in a very close crop to see what's there. I hope you'll be able to see this at full size, which is how I've posted it.

Olly

Quite amazing detail given how close the crop is! I suppose this is pre BlurXT too?

3 hours ago, GalaxyGael said:

Depends on your imaging preferences and how to tackle each night. Fsq85 is arguably easier overall if you get a good sample, but osc-only imaging as I do benefits from speed and wide-ish field. You get all the tones and colour NB does not, with the option of adding to it if you wish. But to be fair, it depends on the types or targets. For those focal lengths, are you nebulae in broadband, galaxy clusters, dust, or?

Both need setup time at the beginning. But fsq85 small star shape is fine with 2600mc with the 1.01x flattener. I know it's also perfect with 5.94um pixel full frame imx410. Extreme astigmatism comes from miscollimated fsq85 that shows more with small pixels, and that is more common than you think and takes a lot of time waiting for repair. With a good sample, assuming the focuser doesn't have slop, the fsq85 is very sharp. New reducer looks tempting, but the fsq85 with modern sensors is back focus sensitive, no way round that unless you go backwards in sensor tech and size. There are easier lens systems with in built flatteners around if that matters to you.

Now star shape....Rasa never appealed to me in that department, but it gives signal at the fl unmatched by almost nothing else. That matter to some, maybe you?

Fsq85 to me is worse. Cat eye bokeh from the virtual field stop of lens 3 in the stack that gives almond shaped out of focus stars and causes cracked stars, or inverse dark lighthouse beam effects in focus. These used to be hidden behind stumpy little 'newtonian-esque' spikes in older cc'd cameras with bigger pixels from the significant periodic texture of microlenses on the side that the light hits. With planar back side lit sensors, you'll see huge unavoidable dark beams that rotate around the frame, markedly pronounced with osc cameras in broadband where the stars are not suppressed like NB imaging. To me, it's worse than any system with diffraction, and from a scope where stars should be round. And it gets even worse if you do mosaics where they don't line up etc.....Do you need round stars? There are better apo out there for that. 

But, there are too many decent triplets with flatteners that work at f4.8 now, and even the 110mm flat field options that are almost identical to the AP 110gtx in design (can't say anything about execution). Esprit 100 is a great example of similar focal length, round stars and good sharpness tbh.

The FRA300 in a good sample is fantastic, very easy setup and the whole thing melts in to the background. Probably since it is small and tidy, but corrects 2600mc and larger.

But from my experience in bortle 6, and knowing others in bortle 4, osc imaging is better with fast optics. You're forced to use shorter subs (balancing zero gain options to use the whole full well capacity too), which takes care of stacking statistics, and you can get an image in broadband or NB in a single night.

To balance that, I quickly realised that fast optics tempted me to image the same duration as I used to, but get what F5/6/7 refractors could not in a sensible amount of time - depth. I'll caveat that by saying its not general, and big aperture, long focal length, big pixel systems are not so f-stop dependent. So a tak epsilon takes the same imaging time for me over a few nights after owning it for a while, but I see more because it can do that at a decent pixel scale with high snr. That's what happened with me, though...

Fsq85 is fantastic in NB, but you may get such good data that you realise you want more to complete an image given it's relative speed. For osc targets only your image quality preferences will dictate whether one winter night will be sufficient. It can be from f3.3 down to f2 though.

The fast mirror scopes have their limitations as you know, and paying for the stable collimation options is a hurt-once problem, but takes that nightly concern away. and some of the concerns you read about online are sample variation, but an OSC camera setup are a little less taxing on a focuser compared to the mono setup with additional components. Aperture resolution benefits at short FL are in the weeds, and I doubt you will see night and day differences sufficient to be swayed by that criterion alone.

Thanks for the informative, detailed reply. I guess my main interests at this focal length are nebulae, both in broadband and with a dual narrowband filter, and the dark dusty nebulae that have become more popular recently. As I write that, it’s  obvious I should prioritise signal over everything else. Especially, since I’m rarely collecting more than 4-6 hours on one target. Also, I notice I’m pushing my images too far when processing. The remedy to that is likely more integration time or something that collects signal faster. 
 

Interesting comments on the Tak star shapes. I was aware of the reverse lighthouse effect and it’s not something that bothers me in terms of an aberration or artefact (halos are my pet peeve). Hadn’t heard about cats eye bokeh though. Had a look online and see its inherent of the Petzval design. Is that what the new flattener was/is trying to correct?
 

I’m curious to hear of the other refractors that operate at f4.8 that you think are better than the FSQ-85. And those designed like the AP 110? (I’m in that lottery!).

I’ve learned that I’ll likely be a OSC man with dual narrowband filters. Tried the mono route and had so many unfinished images. I’ve also learned that weight and complexity of set up hinder me. Had an EQ6R and could never be bothered to take it out. Now have a Rainbow RST and with the Askar FRA400 I’ve never been so productive, albeit I feel I’m lacking something in my images.  

The comments here are largely pro RASA, or fast reflector of sorts. I think my main worry is that if the set up ends up being a nuisance I’ll give up. However, won’t know until I try. I think I’ll probably just sit on this until later in the year as come April the night will already be short. That gives me a chance to keep an eye on the market for a deal. 

10 hours ago, gorann said:

RASA any day! So much deeper and therefore you get more to show and more to find, including the occasional new finding. Will not happen with the Tak in a reasonable time. If you want refractor stars from a RASA just do BlurXT to get the shapes and then Unsharp Mask on the star layer to get the pinpoint look, although personally I am kind of soft on soft stars as they do not distract so much from the nice nebulosity you are looking for. Who are imaging to primarily image stars?

You certainty are prolific with it and produce cracking images! It’s not so much primarily imaging for stars. It’s the work involved getting them good enough and if the process would defeat me before I get to that point. 
 

I would love to see 6hrs on a range of targets from both scopes with comparable conditions to see what the difference in a final image would be. Maybe I should buy both and test 😂

11 minutes ago, GalaxyGael said:

There's a few epsilon 160s available in Europe right now just fyi ( but off topic a bit)

Not off topic at all! Where are they available? I’m on a waiting list at Kyoei in Japan, where the Tak gear is available quite a bit cheaper than Europe. Since I have to deal with customs wherever I order from it makes sense for me to order from there. 

3 hours ago, Adam J said:

Now the FRA300 has a wonderful spot diagram, one of the few scopes that by claim at least would make use of 2.3um pixel cameras. 

Adam 

I agree the FRA300 looks great but then I’m surprised you think the FSQ has poor performance with the new flattener. Looks better corrected and smaller spots than FRA300 although can’t find any quoted RMS radius. The new reducer for the Tak does quote spot size though and it’s 1.6micron on axis, 1.9 at APSC and 3.9micron at full frame. Of course price difference aside.

2 hours ago, Adam J said:

OP is making an argument that 200mm aperture will resolve more than a 85mm refractor..am not so sure that true, I would say that for most of Europe unless you are at significant elevation both will resolve the same due to atmospherics

 

 

I wasn’t making an argument, I was asking a question. I was curious to know, based on my local conditions what would resolve more detail and provide a sharper image.

1 hour ago, ollypenrice said:

Do you find anything to reproach in this level of visible detail from an instrument of 400mm focal length? I don't. What does the OP think?

Olly

I certainly do not, and your images as well as your apparent change in stance regarding such scopes is part of the reason they interest me. However, I see the other side too. I am interested in spot diagrams and star shapes. I’m looking for the right balance of going deeper in my limited imaging time but getting the most from the optics in terms of sharpness and star shapes. It’s also about me choosing something that fits my habits. 

The sampling rates and FL of both are fairly similar so maybe there is a quasi-objective answer of what would provide the more pleasing image.

Anyway all good input, don’t know if it’s made a decision any easier for me though 😆

13 minutes ago, iantaylor2uk said:

I would recommend the FRA 300. I know you have the FRA 400 and could use a reducer, but from my point of view the whole idea of these short focal length refractors is not to introduce any more glass, so I deliberately chose the FRA 300. I have matched it with a ZWO 071 MC Pro camera - although this is not the latest tech it does have quite large pixels for a CMOS camera (4.78 microns). I have found this to be a pretty good combination, and I consider f/5 to be fast for a refractor (my other one, a Tak TSA 102 is f/8!). I have also had some great results from this combination too. 

Very nearly bought the FRA300 when I ended up with the FRA400. Probably should have tbh as it seems to have tighter stars than the 400. Still, I think I would prefer 400-500 now as I’ll use the Samyang 135 and have a Tak TSA120 at nearly 900mm FL. Seems like a nice set up, I’ve seen some of your images 👍

4 hours ago, geeklee said:

It's not so much the collimation as - hopefully - that's not something you should have to do (often/at all) nor want to on an expensive F2 system!

For me, it's the margin of error for what you consider "good enough"  This is vasty subjective and no different it seems for RASA images - where speed is king.  If you do need to tweak things (whether that be collimation or some tilt etc) and have minimal clear nights like a lot of us, could you see yourself sticking it out?  How good will be good enough?

I take it size and weight aren't a factor for yourself or mount?

With two scope options ranging from F2 to F3.6 (with reducer) and a possible budget of ~£2.2K to~ £3.1K you've got a big margin there - could anything else sit in that gap?  How critical is the speed as - again - that's quite a difference in aperture/speed with the two options.

It sounds like most of these are the items you've already thought about!  

Yeah it seems like the RASA will give you back what you’re willing to put in and that may be where I fall down. I would absolutely set out with the right intentions but I know if it starts needing more fiddling than the initial set up I will give up. I’m definitely open to more suggestions if you have any. For instance the aforementioned Epsilons are interesting but may present similar problems as the RASA. The new WO Pleiades look interesting but I’m not sure I’m ready to be an early adopter. Maybe a used FSQ106 could be an option?

In terms of size and weight it has to go on an RST135 so RASA8 size and weight is probably max. It doesn’t have to be the fastest but I see on average that I collect 4-6hrs data per night (from Bortle 4) and as I rarely get consecutive clear nights that’s usually all I’ll collect on one target. So, it doesn’t necessarily need to be F2 but the faster the better.

1 minute ago, Elp said:

If you want the sample the speed and you don't already have one consider a Samyang 135mm F2 lens. Don't think because it's a camera lens it's no good, it's one of the best AP pieces of equipment I've ever used, better than a lot of scopes for raw speed, size etc. You do get tilt issues and perhaps lottery in quality, I've got two used and both are fine. I'm actually thinking of a third...

I have one. That will be my super wide field and travel rig. 

47 minutes ago, Adam J said:

I can honestly and whole heartedly say i would personally not buy either scope. The flat field on the 85 is disappointing for a scope of its cost and the F2 RASA has always seemed like too much compromise in other areas (filters, difficulty using mono). 

If spending that kind of money and wanted to be at 400mm focal length I would 100% without a doubt go with an Epsilon 130, no problems with filters and no problems with mono. 

 

Adam 

I’m actually on a waiting list for the Epsilon 160ED but have been told it will likely be years before it materialises. The 130D seems as scarce these days. I’m not sure it would be any easier getting dialling in an Epsilon over the RASA. Although image circle and field correction should be better. Not quite as fast though. 
 

Are you saying the flat field on the FSQ is not good even with the new flattener? When I look at the spots and some examples I’ve seen on forums it seems pretty much as good as it gets at this FL with a refractor and the IMX571. The new reducer looks fantastic too. That being said, you are paying a premium and not guaranteed the performance. The Vixen VSD90 looks like it may have the best correction and performance but it’s more than I want to spend. 
 

I’m not ruling out ever going back to mono but I plan to stick with  OSC at the moment so the filter issue doesn’t affect me. 

1 hour ago, fwm891 said:

I have an 8 inch RASA and have just acquired an Askar 120 APO with 0.8x reducer flattener. I capture with an ASI 2600MC Duo on both the FoV of the RASA is larger (3.36° x 2.25° v 2.00° x 1.34°).

Personally I've had no problems with collimation with the RASA. Your biggest problem with the RASA will be fitting filters and retaining image registration if you have to remove the camera to fit a filter. There are filter drawer units for cameras with 6.5mm back focus (asi533MC) the 2600MC has a 17.5mm back focus there are filter slip-in units which means you retain image registration. Not sure where you would find them in the UK.

I have the 120 APO permanently mounted in a obsy the RASA I now use as a mobile scope so I can get the most photons in the shortest time available.

Note: your FoV with the RASA is fixed. With the 120 APO you have the 1x and 0.8x options...

Thanks for the opinion. Seems like yours is like most. If you can work with the quirks and deficiencies of the RASA it seems most are happy. I’m maybe just a bit too apprehensive of leaving my refractor comfort zone. 

3 hours ago, Stuart1971 said:

I will give you my experience…

I owned a Tak FSQ85 and it was very poor indeed with modern small pixel cameras, even with 2 flatteners it was still pretty bad, and why should you pay a premium for a 4 element Petzval design scope with built in flattener, and then have to add a second flattener on the back, and have all the backspacing issues that you should have avoided with the Petzval design,  it’s a joke to be honest, and the extra flattener gives about a 15% increase in image quality,  at least they now supply the extra flattener in the box with it, as for using a reducer, well, I never even got that far.

If you get a poor example then you are stuck, as there is no option but for it to go back to Japan for adjustment, with approx an 18 month wait.

If you really trawl the internet this issue is very common and they are not all they are cracked up to be…

Fo me the Rasa all the way…..

I was the worst scope I ever owned, and I have had a few

if you want astigmatism in the outer 1/3rd of your images like this, then go for the Tak

 

Thanks for the reply.  think I maybe came across your case when I was looking into the FSQ-85. A nightmare scenario for you and one I would hope to avoid. It does seem it may have been a collimation issue though? I’d hope if I bought new I would be able to return rather wait for a lengthy repair. I’m aware I could end up in a similar scenario though, but as @Elp mentioned, the RASA’s have had their fair share of issues as well. I guess any scope is a little bit of a lottery, even the supposed premium offerings. I do agree it’s frustrating that they had to add a flattener to correct issues exposed by small pixel cameras. It negates the benefit of the native design.

4 hours ago, Elp said:

I don't have a RASA but do image at F2 with a Hyperstar and I can say this, once you image at this speed and resolving capacity with the given aperture you likely won't use anything else as often because everything else will seem too slow. I took this route because of the same issue, limited image time and opportunity.

But, if you are finicky about star shapes that may be an issue. The Rasa is better than what I use, but I setup and break down mine every time and don't even have to look at collimation, the given star field looks good enough to me and the main reason to use it is for target acquisition, not star shapes, but even so it's collimation looks good and it doesn't seem to change, if I have to adjust its no issue so for me I don't see why people fuss so much about collimation on faster systems. A larger sensor may present more of an issue however.

For crisp sharp round stars you can't beat a refractor. I still use mine for star acquisition to combine with the F2 data. I also find setting up a refractor easier on the mind even though both generally take the same amount of time.

If you do look at the Rasa 8, make sure it's from the new batch which have only just come back on market from Celestron after a lengthy more than 12 month quality issue, a reputable seller will know about this and be able to advise. If buying used make sure it has proven imaging capability.

2 hours ago, Elp said:

If you're willing to forgo the F2, and are intending to buy new I'd also consider the Askar 103/120 triplets. Framing certain nebulae can be an issue at such FLs though.

Thanks. It does seem a common theme that people don’t look back when they go F2. Also, from comments I’ve seen it seems issues are more related to tilt and back focus rather than collimation. If these are one time problems I’m willing to work with it as likely is have similar hurdles setting up a refractor initially, although maybe not as challenging. Yeah, my plan if I both would be to get new batch and somewhere that accepts returns if I realise it’s not for me. I have no issues with Askar scopes. I have two and they do what they are supposed to but to achieve the round stars they sacrifice sharpness and I’ve found that it’s bothering me a bit. Maybe I’m asking too much though. 

I don't have enough clear nights to justify the amount of scopes I have so I’m going to thin down, again! I currently have a number in the 250-400mm FL range and I plan to sell them and replace with one dedicated imaging scope to mate with an ASI2600MC
 

Currently, the main contenders are:

Tak FSQ-85 (1.72”/px) 450mm FL, option of 330mm at f3.9

Pro’s
• Proven performer to APS-C (assuming good sample), even better correction with new flattener

• Ease of use

• New reducer looks fantastic at f3.9 and relatively reasonably priced  

Con’s

• Frustrating having to deal with back focus on what’s supposed to be flat field Petzval  

• Risk of sample variation, expensive if collimation out  

• Focuser not good enough?

RASA8 (1.94”/ px) 400mm FL

Pro’s

• Blazing speed

• Resolve more detail with >aperture?

• Cheaper

Con’s

• Collimation

• Not easy to get good correction at edge of APSC?

• Limited to ASPC and will need new filters. 
 

According to MeteoBlue my local seeing is tends to be in the 1.5-2 arc sec range and I’m in Bortle 4 according to light pollution maps. Have no idea if this is the case but in either case the sampling of both scopes seems ok. 
 

More important to me is to make use of the limited clear skies I have. I  tend to not image one target over multiple nights so I want to collect as much as possible in one night! That of course favours the RASA but I need to balance that with ease of use. If there’s regular fiddling to be done I tend to give up and losing a night to issues is more of an issue than what’s gained from the extra photons on the sensor. 
 

I’ve become quite picky with star shapes and sharpness. I’ve been using a FRA400 recently which is easy to use and gives me round stars but images appear a bit soft for me. I’m curious to hear what people might think would produce the sharper cleaner image out of the RASA/ Tak? Baby Q seems tighter with spot size etc but is this offset by the extra aperture of the RASA? I realise a lot of the processing tools we have these days can negate much of the negatives of both setups but I would like the easiest data to work with to start with.  
 

Right now I’m leaning to the Tak but I would say that’s mainly because of my trepidation of dealing with collimation etc. Otherwise, I feel it’s a toss up. 
 

Will cross post this on another site so apologies if you read this twice and thanks for reading and even better if you offer an opinion!

Chris

I had clear skies on a new moon so decided to attempt another dark nebula. Managed to collect 5hrs data on the Shark Nebula with an Askar FRA400 and ASI2600MC. 
 

Always tough finding that balance of bringing out the dust and not pushing things too far. Hopefully, I have!

Yeah it’s a bit daunting when you first start using the software but worth it!
 

There are a few ways, but here I just used Curves Transformation and globally pulled up the saturation. 
 

Is this your first ever image? Even if not it's fantastic. Great shot and more data will only make it better. What did you use for processing?

One thing you might want to look at is the galaxy is a little blown out. I guess you were trying to show the fainter extents of M51? However, in doing so I think you are losing a lot of the detail and colour you have there. I hope you don't mind but I took your image and lowered the highlights in LightRoom, then increased the saturation in Pixinsight and gave it a blast of BlurXterminator.

A lot if this is subjective so forgive me if it's not to your taste but I think you can see more detail here and little bit more of the colour. I think this video from Adam Block is great if you have PixInsight. Otherwise there are other ways. In any case, great image. Thanks for sharing and please post more!

5 hours ago, ollypenrice said:

Magentas arise from too little green. Did you use a green noise remover, perhaps?

Whatever, your results are excellent.

Olly

Yes, I used SCNR at some point in the process. I’ll need to remember that in the future 
 

Thanks! ☺️ 

Fed up of snow ❄️, rain ☔️, cloud ☁️ here so had a bash at the excellent IKO M81 and M82 data set from @FLO. Not done much Ha LRGB processing so this was a good test for me. Fairly happy with it although for some reason the filaments on Cigar Galaxy came out purple/ pink. No idea how I managed that. Grateful that we have free resources like this!

Also, added a widefield shot of the galaxies with Coddington’s nebula that I took with my little Tak FS60 last year. Amazing how much the focal length alters the perception and context of objects!

I would love it if my destruction ended up like this! Great image 👏🏻 

On 01/02/2024 at 18:00, pie_in_the_sky said:

Cheers - yep, looking into it some more I could get a couple of ZWOs for the same price new! That's a good point though about a dedicated astro and a stock camera for daytime. You're right about the DSO - it's probably going to be mainly DSO with occasional landscapes.

It sounds like you're all in on the mirrorless. What took you away from DSLR? Out of interest, what DSLR (modded) would you say is a good option?

Last one, can you expand on the point about scopes not supporting full frame - is this because it results in vignetting or is there something else?

I didn't specifically move because it was mirrorless, just that a modded EOS R came on the market. Before that I had a modded 6D and that is generally a well thought of DSLR for astrophotography. If you say it's mainly DSO stuff you're interested in then I would encourage you to get a dedicated cooled astrocamera instead. I've only used a modded 6D and EOS R, which I've been happy with. Really couldn't say if they are any better or worse than others.

@geeklee covered it regarding scopes not covering full frame. It's just something to bear in mind so you don't shell out on a very expensive full frame sensor only to find out you can't make use of it.

It is a stock camera but the use of an additional Ha filter is not redundant. In fact in some scenarios it will be highly recommended. Although the Ra is more sensitive to the Ha spectrum than a normal EOS R it still benefits from a filter with a narrow band pass to really bring out those Ha emissions. 
 

It sounds like you are more tended towards DSO photography and in that case for the price of an EOS Ra you could have a very good dedicated astro camera and a decent stock mirrorless for daytime photography. 
 

For me an Ra or modded camera really come into their own when you are primarily shooting astro landscapes and might only shoot DSO stuff now and again. Bear in mind many telescopes don’t  support full frame. 
 

There is no doubt that an EOS Ra can be your only astro camera. Check out a guy called Mark Shelley but if you want it do it all it’s not worth the compromise in my opinion. I have a modded EOS R btw. Use it exclusively for astro landscapes. 

2 hours ago, bosun21 said:

He has stated this on many of his videos that he is sponsored by Askar.

Does he say he is sponsored? I have heard him say Askar sent scopes to review but sponsored is a completely different thing. That would definitely compromise objectivity when reviewing. Having said that I’ve always felt he’s impartial when I’ve watched any of his reviews. 

7 hours ago, varius21 said:

Thank you very much! I appreciate your input and suggestions! I will try the above

No problem 😊 I would add one more thing. If you haven’t budgeted for a guide scope/ cam and some processing software I would set aside something for that.