New scope for deep sky imaging

[wouterdhoye]

Hi,

 

i'm in the market for a new imaging scope for deep sky. I'm a bit overwhelmed by the current choice on the market so i could use some help making up my mind.

Let me tell what is important to me:

high quality optics for sure

easy or reliable collimation

Good thermal stability to allow long sessions wit limited or no refocusing

medium long focal length 1000-1500mm

must be portable so weight and bulk should be kept in consideration

Price is not my main concern  

My current scope is an mn190 so i'd like to upgrade from that one. Mount is a paramount mx an the camera is a qhy 163

thanks for some advise.

 

Wouter

[alan potts]

There was me knowing nothing but reading anyway, thinking, what about an M/N 190mm. I have one for visual and it is very good. What about one of the mid-range RC scopes from GSO, I had the small one for a while but I am not sure how the F/L pan out, but believe most use them with a focal reducer of some sort.

Alan

[wouterdhoye]

Hi Alan,

Thanks for the suggestion. I currently own the MN190 so that is in fact the telescope I'd like upgrade from. I'm a bit reluctant to conisder an RC from GSO or any other make for the fact that I read too many horror stories about RC collimation. A good solid newtonian might still be an option as these can be collimated quite well during the day. (aser/autocollimator) I believe that is not the case with an RC and this would cost precious observing time when using the telescope at a dark site. Offcourse I mayeb should not believe all I read on the inetrnet either

Kind regards,

Wouter.

[swag72]

Here's my thoughts - limited a they are

1-1.5m is a tricky focal length to get all of the things that you want in my opinion. High quality optics and easy collimation leads me to a refractor (ie - No collimation  ) but you are never going to find an easy to carry and portable one in that focal length. 

I get what you read about the RC's and they are a nightmare to collimate, but I had one and was scared to death how difficult this was going to be and with a Cheshire it was easy.... but that is not to say that would happen in all cases, perhaps I just got lucky! 

An EDGE such as the 8" would fit into many of those categories that you mention, but I'm not totally convinced about the optical quality.

Now I did have an 10" ODK for a while and that was a great scope... pretty easy to move around as well.

I think that there will be compromises to make in your choice sadly.

[wouterdhoye]

Hi Sara,

Thanks for chiming in. A high end refractor is indeed high on my list, instruments like a Tak TOA 130 are for instance still in my list of sufficiently portable instruments. 

Anyone here with experience with the APM 152 f/8 doublet? A 150mm triplet is unfortunately a bit too expensive. Or would I certainly be better with a 130 triplet if I go the refractor route?

Kind regards,

Wouter.

[swag72]

Ah well..... I have a 152mm TMB triplet and I would not consider it portable in any way.... it's nothing short of a monster. Based on my experience of that, that was why I thought you'd be discounting a refractor..... But if it's an OK size, why not consider a TEC140  

[ollypenrice]

I'd go for an apo refractor. They are not 'easily portable' in terms of being small but they are easily portable in terms of being manhandled without complaint. This matters. Optical quality is excellent so, although a 140/150 apo would be at the lower end of your focal length spec, the quality would make presenting images at full size easier.

There is no scope which can be sure to run all night without refocus but you are unlikely to beat a refractor in terms of stability.

A second hand TEC 140 should be available for around 4000 Euros - but mine isn't for sale! (Oh the very idea!!) Other big apos come up pretty regularly, too.

Olly

[swag72]

How about a Skywatcher Esprit 150........

[ollypenrice]

54 minutes ago, swag72 said:

How about a Skywatcher Esprit 150........

Great scope.

Olly

[steppenwolf]

Obviously, I have a bias here as I own one but I'd put the Esprit 150 firmly on your shortlist as the optics are fantastic and with the recommended field flattener (specific to this telescope) you will achieve one of the flattest fields I have ever come across. It isn't 'light' but it is substantial and unlikely to get damaged or knocked off collimation in general transportation and it is a well designed triplet so chromatic aberration is exceptionally well controlled.

The TEC 140 should also be on your shortlist but you'll never prise Olly's from him!

[swag72]

I am a great refractor fan and can finally reach that conclusion having tried an SCT, RC and ODK at a longer focal lengths. I have now accepted a compromise of sorts with regards to focal length and have a focal length of 1200mm covered with the most gorgeous refractor that I don't think will ever be prised from my clutches  

I have personally found the refractor to be something of a monster as I already said, but as Olly and Steve say it is going to be the most stable and forgiving with regards to transportation. I'd say have a look at a large frac if you can and if it is not too big for you then that would be an idea scope! Sure its not the fast F ration that folks go on about...... but the perfect scope that covers ALL bases is either just not out there for the majority of us or is just so prohibitive in its costs.

[wouterdhoye]

Thanks people,

sooooo.... a high quality apo it will be.

options within my budget:

tak toa 130

tec 140 (barely)

esprit 150

WO flt 132

Am I missing some? I doubt there is much to go wrong here... not making it easier. Do all these scopes need a field flattener for a 22mm diagonal sensor?

Wouter

 

 

 

[steppenwolf]

7 minutes ago, wouterdhoye said:

Do all these scopes need a field flattener for a 22mm diagonal sensor?

YES!!

[swag72]

Just now, steppenwolf said:

YES!!

What camera is a 22mm diagonal sensor? I ask as I am not using a flattener on the TMB with the KAF8300 sensor and I know of an Esprit and a couple of APM 152's that are not using flatteners with Sony chips......

[steppenwolf]

I tend to recommend their use in refractors generally as the curvature errors start as you move away from on-axis even though they are not readily apparent so to me it makes sense to correct the field from the start even though the perimeter stars may look tight.

[Chris]

6 hours ago, swag72 said:

An EDGE such as the 8" would fit into many of those categories that you mention, but I'm not totally convinced about the optical quality

What are your concerns regarding the Edge HD, Sara? Reading the OP remit an Edge 8" with 0.7 reducer fit's the bill quite nicely. Out of the handfull of SCT's I've owned and used the Edge was the best, sharp and flat with good build.

I'm guessing the Esprit 150 or Tec140 would be nicer admittedly   

[ollypenrice]

My Atik 4000s had a 22.8mm diagonal and showed slight distortions in the corners with the TEC. I decided that this was tolerable given the price of the flattener! I just wrote a Ps 'star rounder ' action. When I moved to full frame CCDs the flattener became imperative and also, I found, improved the imaging performance by enhancing the control of the blue channel. This effect has been noted in a CN thread as well. With flatttenr the field is incredibly flat and evenly illuminated.

Olly

PS, quite honestly, out of your shortlist, I'd probably go for Esprit if buying new.

 

[Gina]

If the Esprit is as good as the 80 I would agree.  I have been very impressed with my Esprit 80ED

[swag72]

51 minutes ago, Lockie said:

What are your concerns regarding the Edge HD, Sara? Reading the OP remit an Edge 8" with 0.7 reducer fit's the bill quite nicely. Out of the handfull of SCT's I've owned and used the Edge was the best, sharp and flat with good build.

I'm guessing the Esprit 150 or Tec140 would be nicer admittedly   

Personally, a large majority of the images that I see with the EDGE always seem a tad on the soft side and the stars always look a little big. While my SCT wasn't an EDGE version, I found the same issues. 

[Chris]

14 minutes ago, swag72 said:

Personally, a large majority of the images that I see with the EDGE always seem a tad on the soft side and the stars always look a little big. While my SCT wasn't an EDGE version, I found the same issues. 

I think you've got a more refined eye than me, Sara. I've just re visited the Celestron Edge gallery on Flickr and the images look great to me. Each to their own  

 

[swag72]

5 minutes ago, Lockie said:

I think you've got a more refined eye than me, Sara. I've just re visited the Celestron Edge gallery on Flickr and the images look great to me. Each to their own  

 

I doubt it!! I just have a slight bias  

[ollypenrice]

3 hours ago, swag72 said:

Personally, a large majority of the images that I see with the EDGE always seem a tad on the soft side and the stars always look a little big. While my SCT wasn't an EDGE version, I found the same issues. 

I agree. I do have a Meade ACF awaiting long overdue field trials and I wouldn't have bought it if I didn't think it had potential, but if you want tight stars I'd go for a refractor. Stars are very processing-intensive. When you see great images from any system beware the skill of the imager! Go with what most of the images look like.

Olly

[wouterdhoye]

Hi everybody,

can I say that the conclusion is this?

Either a second hand Tec140 (if I can find one) or a new esprit 150

Both will need a flattener (this appears to subtantially cheaper for the esprit)

What about focusers, not unimportant I guess. The with the Tec I certainly can be confident as it is fitted with a feathertouch. How good is the focuser on the esprit? Can all connections be threaded? I believe the focuser can rotate.

What about focuser automation? I was looking at the systlem from starizona. They have dedicated kits for both FT as well as esprit.

kind regards,

Wouter

[pete_l]

One of your criteria was "weight and bulk should be kept in consideration". Bear in mind that the Esprit 150 weighs more than your existing MN190 and both it and the TEC140 about the same length as what you already have.

[wouterdhoye]

Hi Pete,

The length and bulk are still within my tolerances. The length and weight of the MN190 have never bothered me. The Esprit 150 is somewhat heavier but bulk is about the same.. as long as it is not something like a 12" f/6 newt or bigger/heavier I'm sure I can handle it 

Kind regards,

Wouter