So close to ordering, but then...

[AKB]

1 hour ago, Waldemar said:

not as big as Celestron suggested in the beginning (70 mm)

My understanding was that this was only for the 14" 'research' version of the RASA?

[Waldemar]

I never heard of that...

Celestron stated the RASA had a 70mm imaging circle, but a few months later they came back on it, saying 44 mm totally corrected and 52mm 'usable'

The dedicate filter has a 68mm opening

I checked it but can't find anything about a 14" 'research' version. Maybe you got more info about it?
If so, please send the file.

Thanks

[AKB]

23 minutes ago, Waldemar said:

I checked it but can't find anything about a 14" 'research' version. Maybe you got more info about it?

It's mentioned in this paper (see Table 1) http://www.amostech.com/TechnicalPapers/2015/Poster/Ackermann.pdf

See, also, this thread on another forum: https://www.cloudynights.com/topic/552249-14-rasa/

...also elsewhere if you look carefully.

[Datalord]

I am bewildered. 

Ok, I really, really want NB. Baader ufc should work. That leaves me to choose a good camera for this setup (budget approx £3k+more for filters). Any suggestions? 

About tinkering, I'm not averse to moping about with the setup, software, buying "things" , but if I have to start making custom components I'll flip tables. If that is required to make this scope work, I guess I'm out.

I just looked at the starizona. How do I attach and control that? 

[Datalord]

So, this might be insanity, but if I use a very high MP OSC, such as the qhy367, combined with a Ha filter, I'd get an effective 9MP resolution. With the very fast scope of the RASA, the integration times should be quite ok. Am I far off?

[Waldemar]

A custom adapter can be made for not too much. Mine was made by Teleskop Express in Germany according to my drawings. Costed me € 240. Not bad...
Starizona:  The motor is dedicated to the FeatherTouch focuser that is on the RASA. To operate is automatically or by hand you need this: http://starizona.com/acb/MicroTouch-Autofocuser---Wireless-P1041C745.aspx  or the wired version which is a bit cheaper. The price includes the low profile motor, which can be choosen in the options section at the bottom of the page. To control it you can you use the included software FocusMax v 3.8 or upgrade it to V 4 which has more options.

As for a camera: http://qhyccd.com/QHY163.html or QHY29 or Starlight Xpress cameras. Many are available, CMOS or CCD, for you to choose.
i would go for full frame and smallest pixels to take full advantage of the scope.

The Starlight Xpress TRIUS SX 36 is expensive, but very nice, slightly bigger then innate obstruction.
filterdrawer system from Teleskop Express in Germany. The site is off line at the moment, but look for the 10 mm drawer system for 50,4 unmounted or 2"mounted filters.
the mounted filters have a narrower opening, but if mounted right in front of the camera that will be no problem for full frame

Filters from Baader (mounted 2") or Astronomik (unmounted 50,4 mm)

For full frame sensors, you will need a custom made adapter, but like i said before, no need to figure that out yourself. Once you decided which camera and drawer system, I can make a drawing with sizes for you and TS will make it. Takes about three weeks. Of course there are more who can make it, but the Germans are the cheapest.

[Waldemar]

1 minute ago, Datalord said:

So, this might be insanity, but if I use a very high MP OSC, such as the qhy367, combined with a Ha filter, I'd get an effective 9MP resolution. With the very fast scope of the RASA, the integration times should be quite ok. Am I far off?

That is what I think as well :-) 

[ollypenrice]

Before going down the Hyperstar route I'd take a look at lots of images produced by the scope other than those cherry-picked by the vendor. You may find you generally like the look of them. Personally I usually don't because I don't like the stellar images. There are exceptions but it safer to judge a setup by its average performance. There are people who can make anything work, but I'm not one of them. I also feel that the Starizona advert is disingenuous, implying that the Hyperstar makes things easy when I don't believe it does.

Of course the other way to go fast, a way which is catching on increasingly, is the dual rig. Short FL optics can be fairly inexpensive but, of course, you do need two cameras. You don't necessarily need two filter wheels though, and certainly not two motorized ones. (NB and luminance runs are always long so if one camera had just manual L and Ha and the other had automated RGB you could scroll RGB,RGB,RGB on one side and bang away in just L or just Ha on the other side.

Here's our dual rig. It is very productive. Both telescopes and the mount were second hand.

This 9 panel mosaic had only three 'observatory hours' per panel. (That's six hours of data, an hour per colour and three hours of Ha.) A number of SGL members have gone down this route which is, by definition, worth one F stop over a single version. It combines some of the advantages of a fast astrograph while preserving the simplicity of refractor imaging.

I would never use pixel count to define resolution. Resolution is measured in arcseconds per pixel and derives from focal length and pixel size. Calculator here: http://www.12dstring.me.uk/fovcalc.php

Chip size determines field of view.

Olly

[Waldemar]

Yes, I think too that the HyperStar is overrated. I used to have one on a C11, but have never been happy with it. Quite a hassle to get good collimation and the 25 mm imaging circle is a bummer. Outside of that quie some aberration shows itself. APSc if lucky, but that is the absolute limit.

That looks really nice Olly and I can see the advantages of that as well. It is all a matter of preference.

@AKB Thanks for the files, I was not aware of the 14" RASA. Not available to the general public, though.

[Datalord]

26 minutes ago, Waldemar said:

That is what I think as well :-) 

I'm so tempted to go this route... 

[swag72]

1 hour ago, Datalord said:

.....About tinkering, I'm not averse to moping about with the setup, software, buying "things".......

Here's my immediate thoughts on this..... I am sure that there are many folks who are not adverse to tinkering ... but think about how much tinkering has to be done during the night..... Are you prepared to give up imaging time for tinkering? I am not and so I've gone for refractors now for a few different reasons....

If I was in the UK on short amounts of imaging time, the last thing I'd want to do with my clear dark nights is tinker and fettle..... I'd want the setup to be productive and remain so in the shortest possible time frame.

Just my boring 2p worth!!!

[Waldemar]

Tinkering in imaging time is not a good option. It should be done during daytime, once it is dark everything should work as it has to...
Almost everything can be tried out and tuned in daylight, except for autofocusing, platesolving and alignment,
but all technical things should be daytime issues.

Even automated imaging can be tried out with a pinhole in the lenscap.

I can state that because I am a major tinkerer  and all of my equipment works just fine at night time by doing what I just said.

[swag72]

I find any tinkering gets done at night as that's when things fail to work for some inexplicable reasons.... to that end I keep it simple  

[ollypenrice]

53 minutes ago, swag72 said:

I find any tinkering gets done at night as that's when things fail to work for some inexplicable reasons.... to that end I keep it simple  

...and you use a dual rig for extra speed!

Olly

[Datalord]

Ok, I'm most likely to go rasa+qhy+astrodon lpr. Then add the manual filter changer and an Ha. 

So, final question: is the qhy367 worth $2000 over the 183 in this setup? It's a lot of money for those extra 16 MP. 

[Waldemar]

It is not only about the number of pixels...

It is the fov that comes into play here... The 376 has a full size sensor (36 x 24mm), while the 183 is only 1" (13,3 x 8,9 mm), but has far smaller pixels...
So more use of the widefield advantage of the RASA with 376, more resolution with the 183...

More differences: 376 needs wider opening, so the M48 adapter is not really an option if you want to prevent vignetting. No issue for the 183 here.
Filters have to be larger as well, I would recommend 50,4 mm unmounted filters or  2" mounted, while the 183 gets away with smaller ones, note that the Baader 'fast' filters are not available at the time...

Especially if you want to get a go at Ha with an OSC camera, the smaller pixels would be better. There will be some special processing needed, I would think.

Always pros and cons... choices...

[Datalord]

Thank you, Waldemar. Your help on this thread had been invaluable. 

[Waldemar]

You are very welcome. If you need a drawing for an adapter or whatever, just let me know.

 

[AKB]

Just to say that to make up the length with my Baader UFC on the Hyperstar, I have a UFC S70 Varilock extender, which gives me an adjustment range of 15-20 mm to accommodate a number of different camera backfocus lengths.  No other 'custom' adapter required. This is an off-the-shelf solution provided to me by Simon at the Widescreen Centre.

[Waldemar]

19 minutes ago, AKB said:

Just to say that to make up the length with my Baader UFC on the Hyperstar, I have a UFC S70 Varilock extender, which gives me an adjustment range of 15-20 mm to accommodate a number of different camera backfocus lengths.  No other 'custom' adapter required. This is an off-the-shelf solution provided to me by Simon at the Widescreen Centre.

Yes they are great. Two lengths are available, but the downside is they are only available in T2 (M42)

[AKB]

9 minutes ago, Waldemar said:

Two lengths are available, but the downside is they are only available in T2 (M42)

No, I don't think that's right.  The telescope-side adapters (various lengths) of the UFC goes up to 65mm diameter, and there are 4 Varilock S70 lengths available.  That's what this seems to say, anyway...

http://www.baader-planetarium.com/en/baader-ufc-(universal-filter-changer).html

[Datalord]

5 hours ago, Waldemar said:

You are very welcome. If you need a drawing for an adapter or whatever, just let me know.

 

I ended up going for the QHY247. APS-C sensor, 24 MP and 3.91um pixels seemed like a good compromise between the 183 and 367. I have no clue whether I need an adapter or not for that.

[Waldemar]

6 hours ago, AKB said:

No, I don't think that's right.  The telescope-side adapters (various lengths) of the UFC goes up to 65mm diameter, and there are 4 Varilock S70 lengths available.  That's what this seems to say, anyway...

http://www.baader-planetarium.com/en/baader-ufc-(universal-filter-changer).html

You are right, I was not aware of this, thought you meant these: https://www.firstlightoptics.com/adapters/baader-varilock-29-lockable-t-2-extension-tube.html

[Waldemar]

4 hours ago, Datalord said:

I ended up going for the QHY247. APS-C sensor, 24 MP and 3.91um pixels seemed like a good compromise between the 183 and 367. I have no clue whether I need an adapter or not for that.

Great choice! At this moment I can not find the backfocus distance of this camera,
I will come back on it later on today, when I am fully awake and after I contacted QHY

[Waldemar]

Thank you AKB for the link to the Baader UFC system!

I was not aware of the Baader UFC S70 system ... I was focused on the filterslider system of Teleskop Xpres...
Apparently the Baader UFC is a lot better with more options. No need for custom made adapters with that system!
I am gonna change my set up to that system, too. Thanks again!

DATALORD:

Not everything is available @ Baader at the moment: The RASA adapter is not in stock and neither are the fast NB filters...

You could use the wider band types like 7 (or 12)nm. The wider band will compensate for the bandshift because of the steep light cone. Basically that is what Baader does, too.

Did not hear anything about backfocus of your camera of choice from QHY, yet... But most cameras in that list have a bf of 18 ± 0,5 mm, so I guess the 247 is in the same line.  EDIT: found back focus figure. The above is correct.
If so, this is what you will need for the RASA with a backfocus of 72,8 mm without the original adapters.
(there is also the possibility to use the M48 original adapter of course, if so you won't need the RASA adapter and skip the 15 mm extension, but order the M48 scope adapter with female connection 245 9129)
1 x 245 9110 UFC Base                                  13 mm                  €  50
1 x 245 9126 RASA adapter                              3 mm                      95
1 x 245 9145 Varilock 15-20mm                 15-20 mm                      92
1 x 245 9141 5 mm extension                          5 mm                      25
1 x 245 9142 15  mm extension                      15 mm                      29
1 x 245 9117 M54 x 0,75 mm camera adapter   2 mm                      28

And then of course the filter sliders themselves:
 ? x 245 9112 filterslider 2"mounted (M48)     € 40 each  Other types are available:  50,4 mm unmounted, 36mm, 50x50 mm, 1,25...

You will have to add 1/3 of the thickness of the filterglass to the optical path.
Since the Varilock has a 5mm range, I don't think there will be any issues. You will have to find the sweet spot anyway by using the Varilock.
A very nice program to help you finding the exact back focal distance is CCD-Inspector:  http://www.ccdware.com/products/ccdinspector/