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Which Apochromat for DSO imaging on an AVX?

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#1 luter68

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Posted 07 September 2018 - 08:12 AM

Hi,

 

I am sorry to ask yet another version of such a question. However, after having done all possible homework, I am still undecided and I would really appreciate some help/suggestion. Also critical comments on my reasoning to come down to the scopes I am debating about, is more than welcome.

 

What I am interested in?

DSO photography. As my eyesight is not so good, I do not care, in general, about visual.

As I live in central Europe (about 50 deg North), planets are never such a great target.

I like to photograph the moon, though but it is not a driver (and in any case I have a Mak 127 that I can use for that).

 

Which mount and setup I use right now?

I use an AVX that I need to move to my backyard every time I use it. The mount was chosen for its weight.

As much as I may like a better mount, I am not prepared to carry around more weight or at dismounting everything in bits every time. So, changing mount is not an option for the foreseeable future.

I guide by using PHD2 on an ASI224 with an ASI 60/260 guide scope.

My main camera is an ASI183MM with an EFW8. Currently, imaging is done with a Nikon AI-S 200mm f/4 (front stopped to 37mm). Both systems are mounted on a dual mount plate. The lens is nice and I'll continue using it, but it is substantially a good achromat so I would like to make use of the L filter as well as to have some more reach for smaller objects.

 

Due to the small pixels of the ASI183, I want a fast scope, not much slower than f/5, possibly faster.

An f/4 newtonian would be perfect but, again because of my eyesight, I am not too sure of nailing collimation as required for such high resolution camera (I have never done it in practice, so I do not know how demanding it is).

So, I would like to upgrade to a triplet apo (as I understand a doublet would not suffice for AP) and I came down to the following models:

For guiding. I would most likely use an off-axis system, especially for anything longer than 400 mm main scope.

 

1) WO GT 71/420 with 0.8x reducer (FL 336mm f/4.7) - about 2.2 kg

2) TS Optics 80/480 with 0.79x reducer, maybe 0.75 Riccardi (FL 380-360 f/4.5-4.7) - about 3.1 kg

3) TS Optics 90/600 with 0.79x reducer, maybe 0.75 Riccardi (FL 474-450 f/5-5.3) - about 4 kg

4) Esprit 80 ED with flattener (FL 400, f/5) - about 4 kg - it may be even used with a reducer for NB work..

5) Esprit 100 ED with Riccardi 0.75 reducer (FL 412, f/4.1) - about 6.3 kg

6) TS Optics 107/700 with 0.79x reducer, maybe 0.75 Riccardi (FL 553-525 f/4.9-5.2) - about 6.5 kg

7) TS Optics 115/800 with 0.79x reducer, maybe 0.75 Riccardi (FL 632-600 f/5.2-5.5) - about 6.4 kg

Cost-wise, they roughly rank as 1), 2), 7), 4), 3), 5), 6).

 

I very much like 5) but I am afraid the load could be too high (about >7.5 kg with camera, efw and guiding).

7) uses FPL-51 and is sold at a very good price (less than the esprit 80). There are amazing images taken with it on astrobin, some of them with an AZEQ5... and I would get rid of the Mak in this case (as well as in the case of 5) and 6)).

However, 7) is heavy and also starts to be quite long so it may be too much and starts to be on the slow side. 6) is the most expensive, probably just too much for me. So it boils most likely down to the first four.

 

I have not listed the ES 102 triplets. The essential version would be great, really. However, I have read about possible issues with the focuser and, more important, I have not found any information on a suitable reducer as it would be too slow at f/7 (ideally a 0.7x reducer would be needed).

 

At the end, despite I would have preferred mounting rings, I am giving an edge to the Esprit 80 followed by the 90/600.

 

Any comment, suggestion, would be extremely welcome!! Many thanks in advance!

 

 



#2 bobzeq25

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Posted 07 September 2018 - 10:15 AM

Beware.  You're headed right for the two biggest beginner mistakes.

 

Skimping on the mount.  Getting too big a scope. 

 

If the scope costs more than the mount, at your budget, that's a red flag.  It's more important.  The quality of the best scope will be completely wasted if the mount won't track accurately enough to utilize it.  Your eyes hooked to a smart brain have some tolerance for motion.  .005mm pixels are completely unforgiving.

 

Both weight and focal length count, actually focal length counts more.

 

Concrete suggestions.

 

If you're going to stay with the AVX, you need to pay particular attention to the scope recommendations below, even though you have some experience.  The AVX is pretty marginal for AP, you need to not stress it too much.   Note that the ieq30Pro is both better and lighter.

 

The ideal starter scope in AP of DSOs is:

 

Short.  No more than 600mm, 480 (or less) is better.

 

Light.  No more than 10 pounds, 5 is better.

 

Fast.  Everything you're considering qualifies.

 

So: 1, 2, or 4 on your list.  I recommend them in that order.

 

Other points.  Carrying a mount around assembled is risky, it's all too easy to stress them in ways that they are not strong.  Get started with that guidescope, learning AP is hard enough, you can simplify that way without worry.  Just be sure it's mounted securely (not on a finder shoe).  When you're up and running, you can try an OAG.  This is how most of us have progressed.


Edited by bobzeq25, 07 September 2018 - 10:41 AM.

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#3 Stelios

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Posted 07 September 2018 - 12:45 PM

You have some initial assumptions that I think you need to reexamine.

 

To begin with, there's nothing wrong with an ED scope for astrophotography. That's even more so if using filters each of which focuses separately. I have an ED80 and an APM/LZOS triplet APO which cost 10 times as much. The triplet is better, but perhaps by 5-10%. On an AVX (which I *have*), I would always choose to use the ED80 because the drop in performance caused by the larger triplet's extra weight would much more than offset any gain in quality. Tracking and focus are by FAR the most important things in astrophotography. 

 

Then, the suitability of an AVX depends on the particular AVX (there's huge variability). What's your RMS (with the guidescope)? Any abnormal jumps in DEC while guiding? If you have a "good" AVX, then it's a very convenient and hard-to-beat lightweight mount. If you have a mediocre to poor AVX, you are in for a LOT of frustration and should consider upgrading (there's several alternatives, some a bit heavier, some lighter).

 

The ASI183 has 2.4um pixels. I don't quite get the need for a super-fast scope. Is this for fear of oversampling? Say you get a 600mm scope. That's 0.825 as/px image scale, and unless you have *really* awful seeing, --and even if you do, with the modern low read error cameras--there's nothing wrong with that. If you get a shorter F/L scope (fast... are you in a hurry? The light does get there even at F/7, just takes a bit longer) then you will be locked out of smaller DSO's in practice, other than as small pimples. Use astronomy tools (imaging mode) to see what objects look like in something like 320 mm which you are trying in some of your choices to achieve.  

 

Assuming you stick to your AVX, you should figure on camera equipment + dovetails at about 3 kg, and target no more than a 7kg total. I would pick your #3 *because* of the longer focal length (which you can choose to reduce). Another reason to pick #3 is the high quality rotatable 2.5" R&P focuser.  Focusing, which you'll want to automate, is second only to tracking in importance.

 

Note also that Bob says "480 or less is better." It's better for *learning* as it's more forgiving. It's not better forever. 


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#4 Goofi

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Posted 07 September 2018 - 12:48 PM

I get why you're using the AVX and to me that won't be an issue. I used one for many years and the simple fact is it is easy to haul in and outside, and easy to use. So, moving on to scopes ...

 

For scopes, I'll make 2 different suggestions - but keep both from TS since it's easier for you being in Europe. The TS Imaging Star 80 and TS 86DQ are both high quality scopes, designed for astrophotography with good flat fields.

 

With either scope you'll get between 2 and 3 degree field of view, and a decent image scale. This will be great for nebulas and larger targets.  Since your camera is the mono version, you can do narrowband easily. If you wanted to go for some galaxies too, the TS 86DQ has the longer focal length to help with smaller targets.

 

Just my two cents. It's easier to get a system with the reducer/flattener built in that adding it later.


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#5 Stelios

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Posted 07 September 2018 - 03:36 PM

I get why you're using the AVX and to me that won't be an issue. I used one for many years and the simple fact is it is easy to haul in and outside, and easy to use. So, moving on to scopes ...

 

For scopes, I'll make 2 different suggestions - but keep both from TS since it's easier for you being in Europe. The TS Imaging Star 80 and TS 86DQ are both high quality scopes, designed for astrophotography with good flat fields.

 

With either scope you'll get between 2 and 3 degree field of view, and a decent image scale. This will be great for nebulas and larger targets.  Since your camera is the mono version, you can do narrowband easily. If you wanted to go for some galaxies too, the TS 86DQ has the longer focal length to help with smaller targets.

 

Just my two cents. It's easier to get a system with the reducer/flattener built in that adding it later.

The TS 86DQ is a great $$$$$cope... :)  I still think it's limiting at 464mm F/L, but if that's not an issue it looks fantastic.


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#6 Goofi

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Posted 07 September 2018 - 04:24 PM

The TS 86DQ is a great $$$$$cope... smile.gif  I still think it's limiting at 464mm F/L, but if that's not an issue it looks fantastic.

 I think this is worth expanding on a bit ...

 

Normally, I'd say <500mm focal length is pushing it for targets luter68 stated. However, he's using a sensor with small pixels, and that makes things interesting.

 

Running the numbers for the TS86DQ, you'll see he has a 2.3 degree field of view (rather large), but with 1.0" image scale. That image scale means targets like M51 are possible - but you'll crop the final image (most likely).  So in this particular case - with a camera with lots and lots of small pixels - that TS86DQ will work pretty well.

 

Plus, being a 4-element scope, it's got a flat field and is very well color corrected. Should he switch later to a different camera - it's still a fantastic wide-field scope.


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#7 TelescopeGreg

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Posted 07 September 2018 - 05:31 PM

I also have an AVX mount, and while light enough to move, it's not light enough for me to move it, unassisted, while assembled.  Probably not a good idea even if I could.  And any mount is annoying to disassemble and reassemble every time you want to use it.

 

If your path from where the telescope is stored to where it is used is relatively flat and relatively smooth, you might consider building a small platform with wheels.  Due to a nice canopy of trees, there are no places at my home where I can see enough of the sky to do any meaningful observing, but my neighbor's driveway across the street has good views.  So, with their permission, I roll my telescope across the street and view / image from there.

 

The heavy "leveler" screws both permit the base to be leveled as well as stabilized.  The rubber tires cushion the mechanism from vibration while in transit, but bounce far too much for stable observing.  The "level proxy" is a small platform that I pre-aligned with the top of the tripod, so that when the proxy is level, so is the tripod.  That way I can get everything moved and set up in minutes, and without disassembling any of it.

 

Telescope trolly:
Telescope on wheels 2.jpg   

 

Leveling jack screws:

Telescope_leveler 2.jpg  

 

Level adjustment proxy:

telescope_level_proxy 2.jpg

 


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#8 luter68

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Posted 07 September 2018 - 07:17 PM

Beware.  You're headed right for the two biggest beginner mistakes.

 

Skimping on the mount.  Getting too big a scope. 

 

If the scope costs more than the mount, at your budget, that's a red flag.  It's more important.  The quality of the best scope will be completely wasted if the mount won't track accurately enough to utilize it.  Your eyes hooked to a smart brain have some tolerance for motion.  .005mm pixels are completely unforgiving.

 

Both weight and focal length count, actually focal length counts more.

 

Concrete suggestions.

 

If you're going to stay with the AVX, you need to pay particular attention to the scope recommendations below, even though you have some experience.  The AVX is pretty marginal for AP, you need to not stress it too much.   Note that the ieq30Pro is both better and lighter.

 

The ideal starter scope in AP of DSOs is:

 

Short.  No more than 600mm, 480 (or less) is better.

 

Light.  No more than 10 pounds, 5 is better.

 

Fast.  Everything you're considering qualifies.

 

So: 1, 2, or 4 on your list.  I recommend them in that order.

 

Other points.  Carrying a mount around assembled is risky, it's all too easy to stress them in ways that they are not strong.  Get started with that guidescope, learning AP is hard enough, you can simplify that way without worry.  Just be sure it's mounted securely (not on a finder shoe).  When you're up and running, you can try an OAG.  This is how most of us have progressed.

Thank you bobzeq25, this is certainly very good advice. In fact, did not really had much hope for the heavier scopes....

i keep the mount fully assembled near my living room sliding door. All I have to do is bracing it carefully and move it through the door for about 4 meters, to the terrace where I have marks for tripod placement. Then, I check the Polaris is centered in the polar scope and run Sharpcap PA procedure, followed by 2+4 alignment. It usually takes to me betwen 20 and 30 min to be ready to go. The excellent two star alignment procedure is another reason I like so much this mount. 

 

the gt71 is tempting because I know it would be easy. However, I cannot afford to change scope soon. Wathever I buy now has to serve me for at least a few years, this is why I am pending towards the esprit 80.



#9 baron555

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Posted 07 September 2018 - 07:47 PM

SV80ST


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#10 luter68

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Posted 07 September 2018 - 07:53 PM

You have some initial assumptions that I think you need to reexamine.

 

To begin with, there's nothing wrong with an ED scope for astrophotography. That's even more so if using filters each of which focuses separately. I have an ED80 and an APM/LZOS triplet APO which cost 10 times as much. The triplet is better, but perhaps by 5-10%. On an AVX (which I *have*), I would always choose to use the ED80 because the drop in performance caused by the larger triplet's extra weight would much more than offset any gain in quality. Tracking and focus are by FAR the most important things in astrophotography. 

 

Then, the suitability of an AVX depends on the particular AVX (there's huge variability). What's your RMS (with the guidescope)? Any abnormal jumps in DEC while guiding? If you have a "good" AVX, then it's a very convenient and hard-to-beat lightweight mount. If you have a mediocre to poor AVX, you are in for a LOT of frustration and should consider upgrading (there's several alternatives, some a bit heavier, some lighter).

 

The ASI183 has 2.4um pixels. I don't quite get the need for a super-fast scope. Is this for fear of oversampling? Say you get a 600mm scope. That's 0.825 as/px image scale, and unless you have *really* awful seeing, --and even if you do, with the modern low read error cameras--there's nothing wrong with that. If you get a shorter F/L scope (fast... are you in a hurry? The light does get there even at F/7, just takes a bit longer) then you will be locked out of smaller DSO's in practice, other than as small pimples. Use astronomy tools (imaging mode) to see what objects look like in something like 320 mm which you are trying in some of your choices to achieve.  

 

Assuming you stick to your AVX, you should figure on camera equipment + dovetails at about 3 kg, and target no more than a 7kg total. I would pick your #3 *because* of the longer focal length (which you can choose to reduce). Another reason to pick #3 is the high quality rotatable 2.5" R&P focuser.  Focusing, which you'll want to automate, is second only to tracking in importance.

 

Note also that Bob says "480 or less is better." It's better for *learning* as it's more forgiving. It's not better forever. 

Thanks Stelios. My “dismissing” of doublets is actually again related with scope speed, so let me just elaborate on that. The small pixels collect less photons at equal scope.  So, 2.4 micron pixels collect 2.5 times less photons for unit of time than the 3.8 micron pixels of the ASI 1600. As we are seeing limited, usually 1” to 2”, aperture doesn’t matter in terms of resolution as soon as you are above 70-80mm. Thus you can get the same kind of details in a 400mm focal length scope with the ASI 183 than you do with 800mm and a 4.8 micron pixels camera. This is good for lesser mounts as the one I have. However, as I said, you do get less signal with the small pixels. Besides that, the camera has strong amp glow. It gets perfectly corrected with darks but it limits your exposure time to about 10-15 minutes. I am right now using 10 minutes subs in h-alpha on NGC 7000. The details, 43 subs later, are amazing with my 200mm lens at f/5.4, but this is also a bright target. I would not go slower than this with this camera. There is a long and really exhaustive thread on this camera here on cloudy nights.

 

Now, doublets, because of the residual CA are usually slower than triplets, unless very small like 60-70 mm aperture.

As an example, the famous SW 80ed pro is f/7.5 and even with a 0.8 reducer, you cannot be really faster than f/6.....

i agree with what you say about taking NB (there even an achromatic doublet will suffice) and color filters, but not the L filter with such small pixels, I would think.

 

About my AVX, l usually get between 1” and 1.5” total r.m.s. error. As I am imaging at 200mm (about 2.5”/pixel) I never botherered improving on this and I do not even slightly unbalance to make the scope east heavy. Clearly, if I double the focal I will also need to be more careful.

 

Scope 3 is indeed nice. I actually realized TS sells also a 80/500 “superapo” that seems to have better mechanics than 2. So, yes, it will be one of these.

 

Thanks again.


Edited by luter68, 07 September 2018 - 07:57 PM.


#11 luter68

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Posted 07 September 2018 - 08:11 PM

 I think this is worth expanding on a bit ...

 

Normally, I'd say <500mm focal length is pushing it for targets luter68 stated. However, he's using a sensor with small pixels, and that makes things interesting.

 

Running the numbers for the TS86DQ, you'll see he has a 2.3 degree field of view (rather large), but with 1.0" image scale. That image scale means targets like M51 are possible - but you'll crop the final image (most likely).  So in this particular case - with a camera with lots and lots of small pixels - that TS86DQ will work pretty well.

 

Plus, being a 4-element scope, it's got a flat field and is very well color corrected. Should he switch later to a different camera - it's still a fantastic wide-field scope.

The TS86SDQ looks really amazing, thanks a lot Goofi for pointing out to me this scope and its smaller, but faster, brother. The only issue I have is that I am not finding much in terms of first hand reviews but I will look for more. It is also a trifle on the slow side. What about the 6 elements f/4.4 one in terms of record?



#12 luter68

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Posted 07 September 2018 - 08:18 PM

I also have an AVX mount, and while light enough to move, it's not light enough for me to move it, unassisted, while assembled.  Probably not a good idea even if I could.  And any mount is annoying to disassemble and reassemble every time you want to use it.

 

If your path from where the telescope is stored to where it is used is relatively flat and relatively smooth, you might consider building a small platform with wheels.  Due to a nice canopy of trees, there are no places at my home where I can see enough of the sky to do any meaningful observing, but my neighbor's driveway across the street has good views.  So, with their permission, I roll my telescope across the street and view / image from there.

 

The heavy "leveler" screws both permit the base to be leveled as well as stabilized.  The rubber tires cushion the mechanism from vibration while in transit, but bounce far too much for stable observing.  The "level proxy" is a small platform that I pre-aligned with the top of the tripod, so that when the proxy is level, so is the tripod.  That way I can get everything moved and set up in minutes, and without disassembling any of it.

 

Telescope trolly:
attachicon.gif Telescope on wheels 2.jpg  

 

Leveling jack screws:

attachicon.gif Telescope_leveler 2.jpg

 

Level adjustment proxy:

attachicon.gif telescope_level_proxy 2.jpg

Thanks telescopeGreg. It looks like a great system!! In my case, I keep the mount fully assembled near my living room sliding door. All I have to do is bracing it carefully and move it through the door for about 4 meters, to the terrace where I have marks for tripod placement. The assembled mount and scope, all in one piece, is still fine with the rest of my family but I may get in troubles if I escalate things...



#13 Luna-tic

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Posted 07 September 2018 - 09:57 PM

Of the listed scopes, my vote would be the WO GT71. If you can find one (it's now discontinued), a GT81 would give you a bit more aperture with roughly the same F/L and F/R. I have the GT81 and it's a fabulous scope.

 

As for the AVX, it will serve with a scope like above, but limit your total load to scope, guide scope and cameras. I'm using a Stellarvue F50G guide scope, a ZWO ASI120MM-S guide cam and my Nikon DSLR and the mount handles it okay. If you go with a mini for the guide cam and a dedicated AP camera, you can get the weight down a tad more. At any rate, I'm right at 50% of my mount capacity.  As you collect more sofa change, you can upgrade the mount later, if need be and weight no longer is an issue. I've transitioned to an EQ6R-Pro mount, but the AVX will work. I've done a few unguided single image shots using it and an Edge HD8.


Edited by Luna-tic, 07 September 2018 - 09:59 PM.

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#14 JukkaP

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Posted 08 September 2018 - 05:06 AM

I would buy the esprit 80 from telescope austria. And actually I did buy it there. They will fine tune it for you and check for perfect field.

Look their website for the esprit 80 fine tuning servive. Its just awsome.

I have stoped using and recomending any TS products, as their quality has dropped. There is allways something wrong whit the optics.

I got full data of the imaging field of my esprit 80 when I bought it and all was done whit great accuracy.

The esprit 80 focuser is superb, only thing I miss is inexpensive motorfocus. But now making one my self whit arduino and nema stepper motor.
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#15 RedLionNJ

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Posted 08 September 2018 - 11:19 AM

Since you're limited to the AVX (and haven't explicitly mentioned it's NOT a "good one"), I'd be looking to mount nothing larger than around 80mm aperture and maybe 425mm FL on it. Preferably a shorter FL, either natively or with a FF/FR designed for that particular scope's optics.  And with a sturdy focuser which isn't going to cause additional vignetting and is very, very finely-tunable with no backlash.

 

Beyond that, brand would only likely affect price. If I were in Europe, I would buy from Europe.


Edited by RedLionNJ, 08 September 2018 - 11:19 AM.

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#16 luter68

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Posted 08 September 2018 - 03:39 PM

I would buy the esprit 80 from telescope austria. And actually I did buy it there. They will fine tune it for you and check for perfect field.

Look their website for the esprit 80 fine tuning servive. Its just awsome.

I have stoped using and recomending any TS products, as their quality has dropped. There is allways something wrong whit the optics.

I got full data of the imaging field of my esprit 80 when I bought it and all was done whit great accuracy.

The esprit 80 focuser is superb, only thing I miss is inexpensive motorfocus. But now making one my self whit arduino and nema stepper motor.

Thanks, yes, either in Austria or in the UK where there is an online shop that also offers testing and tuning. However, I, will probably set for Austria as it would be easy for me to reach there if I ever would need servicing. 


Edited by luter68, 08 September 2018 - 03:49 PM.


#17 luter68

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Posted 08 September 2018 - 03:48 PM

Since you're limited to the AVX (and haven't explicitly mentioned it's NOT a "good one"), I'd be looking to mount nothing larger than around 80mm aperture and maybe 425mm FL on it. Preferably a shorter FL, either natively or with a FF/FR designed for that particular scope's optics.  And with a sturdy focuser which isn't going to cause additional vignetting and is very, very finely-tunable with no backlash.

 

Beyond that, brand would only likely affect price. If I were in Europe, I would buy from Europe.

Thanks for your advice. I am not really able to rate my mount. I have read around that 1” - 1.5” is what people usually get and I am there. With my current 200 mm lens it is not an issue as my image scale is 2.5”/pixel. I have seen videos with <1” guiding but i don’t know how exceptional that would be. I haven’t made any fine tuning so far. 

 

About the focuser, yes, I am prepared to invest a bit on it.


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#18 Goofi

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Posted 08 September 2018 - 06:56 PM

Both of the scopes I linked to are newer scopes, so you won't find as many images to judge them by. But, TS stands by their scopes and I have not heard of people having issues with their 4 element scopes. So based on that, I'd say either of those are good, safe bets.

 

The 6 element scope is basically a 4-element, with built in reducer. More glass, but faster.  However, I think for where you are at right now the 4 element is a good choice, and better on cost.


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#19 tonyt

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Posted 08 September 2018 - 08:03 PM

The Esprits are plug and play, easy to use, and the Esprit 80 would work well while the 100 might also be ok - it's a bit heavy but it's short.

 

My AVX is no good for unguided imaging even with a small scope such as the Esprit 80, but it works very well when guided by my MGEN. Unguided more than 50% of 30 sec subs were no good, while I rarely lose any 2 min subs while guiding my NP101is.

 

Here's my setup, note the evil eyes in the background (LED streetlights):

IMG_9751.JPG

 


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#20 the Elf

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Posted 09 September 2018 - 04:50 AM

I am very happy with the TS AP 65/420 Imaging Star Quadruplet on an AVX. Imaging is a sunday walk with this thing. Sample images: https://astrob.in/355067/0/  https://astrob.in/355108/0/

You don't even need a finder scope. Perfect for Andromeda Galaxy, Plejades, Heart, Soul, etc. Flattener is in the scope. But beware: even with this short focal lenght you need guiding on the AVX. Mine has got the huge amount of 60 arcsec p-p preriodic error. By PEC (perriodic error correction saved in the mount) it is reduced to about 20. With an APS-C sensor in the 18MPix range you have 2 arcsec per pixel. Short exposures of 1 minute or less are possible without guiding.

Why do I recommend this scope? Because lenses prices go by diameter squared. If you invest a given amount in a larger diameter it is very likely you get lower quality. This is an APO triplet with the FPL53 glass. There are no cromatic abberations at all. It is not too fast, so forgiving with the focus. The only downside: the 5kg weight of the AVX is too heavy for the small scope, unless you put a guide scope on top. Smaller weights are available for a low price. Think about it!

BTW: I payed less than 700 Eur. Prices are going up and down....


Edited by the Elf, 09 September 2018 - 04:51 AM.

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#21 luter68

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Posted 09 September 2018 - 06:20 PM

I would buy the esprit 80 from telescope austria. And actually I did buy it there. They will fine tune it for you and check for perfect field.

Look their website for the esprit 80 fine tuning servive. Its just awsome.

I have stoped using and recomending any TS products, as their quality has dropped. There is allways something wrong whit the optics.

I got full data of the imaging field of my esprit 80 when I bought it and all was done whit great accuracy.

The esprit 80 focuser is superb, only thing I miss is inexpensive motorfocus. But now making one my self whit arduino and nema stepper motor.

JukkaP, thanks, i was looking at their Website. Can I ask whether you paid for the additional test report? It not clear to me what they do as standard support when you buy the scope and what you get with the extra test you pay for.



#22 luter68

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Posted 09 September 2018 - 06:28 PM

Both of the scopes I linked to are newer scopes, so you won't find as many images to judge them by. But, TS stands by their scopes and I have not heard of people having issues with their 4 element scopes. So based on that, I'd say either of those are good, safe bets.

 

The 6 element scope is basically a 4-element, with built in reducer. More glass, but faster.  However, I think for where you are at right now the 4 element is a good choice, and better on cost.

I did found a thread on stargazerslounge abut the 80 f/4.4 and the outcome was rather negative for two users.

That was rather worrisome. Although the 86 f/5.4 is extremely attractive, really, I am likely going to play safe with an esprit 80.



#23 tonyt

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Posted 09 September 2018 - 09:26 PM

, I am likely going to play safe with an esprit 80.

You could add weight to an existing scope, equal to the weight of an Esprit 100, and see if your mount behaves well or not. If it's not up to the task buy the Esprit 80.


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#24 luter68

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Posted 10 September 2018 - 01:18 AM

You could add weight to an existing scope, equal to the weight of an Esprit 100, and see if your mount behaves well or not. If it's not up to the task buy the Esprit 80.

Yes, good idea, thank you.



#25 the Elf

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Posted 10 September 2018 - 01:19 AM

The mount behaviour is not only a question of weight but inertia. If you get two counter weights and put them as far up as possible instead of one at the end of the bar the over all weight is more while the inertia (the force that stands against accellerating a rotation) is lower as it goes by the distance squared. It is the same thing as the ice skater doing a pirouette by pulling the arms close to the body. The less inertia the better the mount can do a correction, which is in fact a change of speed. All premium mount manuals tell you to do so.

 

@Goofi: I did a long research on the TS scopes. At least one comes with a tilt plate for the camera. Looks weired to me. Can't one build the mechanics in a manner that there is no tilt or do they assume the camera sensor is not perpendicular to the thread? They also sell this for the RC8. And thanks for the explanation of the 6 lens. I phoned TS and astroshop but non of them could tell why 6 lenses. Funny.


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