58 replies to this topic

[Mike W]

I don't think I would put Tele Vue on that list because while they've been in the business for years they just aren't in the same league as those other manufacturers (in terms of the optics, not necessarily for the mechanics). Plus, I don't think Tele Vue is really that serious about imaging. They'd certainly like to be considered for imaging but that's really not their main driver. For example, Takahashi is still actively updating their scopes while Tele Vue's Nagler/Petzval design was basically created back in the film days of imaging. They did do a modest update for their imaging system models (the NP127is and NP101is) but I believe that effort was begun almost ten years ago.
 
That said, an NP127 or NP101 can be a really good performer for visual work, but if you want superior imaging then you may be able to find better or more cost effective solutions. And note that I say this as someone who has had reasonable success imaging with my own NP127is (but maybe my sample of that scope wasn't really as good as they get).
 
To be truthful, however, there are probably lots of scopes that are being produced today that exceed in capabilities what the average user will ever be able to accomplish with them. What I mean is that the tools (the scopes) are probably "better" than what the average workman will make of them and that's probably also true with Tele Vue's NP127is or NP101is (here's looking at you james7ca   ).

I think you are dreaming! Have you seen some of the photos taken with Televue optics on their website?
https://televue.com/...over-cambridge/

Edited by Mike W, 23 June 2022 - 12:09 PM.

[rgsalinger]

Remember even though we are in the Refractor forum, the OP is asking about a 4" refractor for imaging, not for visual use.

 

My TV127is is a superb visual instrument. I love taking it to star parties as it frankly pulls way above its aperture against the SCT crowd. However, this is a very old design (mine is 12 years old). As I posted previously, you can get a wonderful scope for AP use for 2500 dollars. If you use it with a big chipped camera it punches way above it's class as a wide field instrument.

 

I posted a screen shot and the FOV numbers. If you're making an AP recommendation I think that you have to do the same. Astrobin links are a trap because what you often see are cropped images and what you always see if the expertise of the imager. You don't see the raw materials - the data - that went into the end result. That's the objective quality measure, isn't it? 

 

Rgrds-Ross

[Mike W]

Well, the Hubble is an old design too!

[jmfcst]

Sometimes highest quality is not where you expected.

Some doublets and triplets are poor, individual lenses do show variations.

My advice is to get it on the optical bench and just get it tested by a professional.

I had to when my AP performed poorly and I was expecting gold.

would love to here the story behind this AP scope

[Oyaji]

Astrobin links are a trap because what you often see are cropped images and what you always see if the expertise of the imager. You don't see the raw materials - the data - that went into the end result. That's the objective quality measure, isn't it? 

 

 

True, Astrobin pics must be used with an appropriate degree of caution, although nothing like the skepticism to be applied to the statements on CN of fanboys of this scope or that.  Spend a half hour on the Takitis! thread and you will immediately see what I'm talking about. 

 

Nobody to my knowledge posts raw image files; all you are ever going to see is a processed result, whether on Astrobin or any other place such as a manufacturer's promotional materials. Used with proper respect for its limitations, Astrobin is a great place IMO to see real results from real hobbyists with real telescopes.  Another place to see real results from real hobbyists with real telescopes is to look around for web pages where hobbyists display their stuff.

 

As for Astrobin pics being cropped--well, the OP's pics are going to be cropped as well in most cases--stacking subexposures, particularly dithered subs, almost always produces, to one degree or another, areas around the edges of the integrated stack that must be removed. But aberrations will typically show up even after the cropping is applied.  A little pixel peeping can be a good thing.  

 

As for the processing expertise of the imager: you have a point, but no amount of processing skill is going to fix elliptical stars around the periphery of a picture. And on Astrobin there are plenty of pics by people with only average processing skills.  

 

Bottom line:  I'm not saying that Astrobin is the be-all, end-all tool for picking out telescopes, but it is a useful tool, used in conjunction with other tools, such as reviews, hobbyist websites, etc.  Anyway, it certainly has been a useful tool for me.  

Edited by Oyaji, 23 June 2022 - 02:57 PM.

[bobhen]

Guys! Wow! I’m not even half way thru reading this amazing set of responses. This is an great info source of detailed ways to consider this or at least get me pointed in the right direction. So, truly, thanks.

One basis question. Since price seems to be a pretty reliable indicator of quality, for a 100mm refractor, what’s’s the threshold price? I don’t mind paying for quality I can’t yet appreciate, but I also don’t need to impress anyone with a status telescope. So is, say, $3500 sufficient?

Below are just some examples that are under, at or near a budget of $3,500.

 

Again, price is a good indicator of quality. But, from the lower priced retailers, you will still get a very nice scope that will most likely thrill you. As with all things hobby related, if you become an experienced imaging fanatic (as many do) you might appreciate the more expensive brands. If you want the absolute best, they will, like all things of quality, cost more of course. 

 

1) TS: Telescope Service offers some of the best prices with their Chinese 102mm F7 triplet starting around $1,800. And they have more to choose from. These are solid scopes and for many their quality is more than enough, especially for the price paid. HERE is a link. 

 

2) As with TS above, Astro-Tech from Astronomics also offers a Chinese sourced line of refractors. Their AT 115 F7 runs around $1,500. Again, these are solid scopes, and for many their quality is more than enough, especially for the price paid.

 

With a budget of $3,500 you could even get a larger refractor from the two retailers above.

 

3) The Stellarvue 102mm F7 SVX102T runs around $3,100.

 

4) Tele Vue’s NP 101is F5.4 runs around $4,200. Because this is a “4 element” fast F5.4 design you will not need a flattener or a reducer. 

 

5) Takahashi’s TSA 120mm F7.5 runs around $4,800 just for the OTA. However, for a 120mm triplet, the OTA is rather lightweight at 13-pounds and the optics are absolutely superb Canon optics. The 120 also gives you slightly more resolution and image scale.

 

6) Astro-Physics has a new model coming out, a 110mm F6 triplet. The price has yet to be determined and if you want one you will have to sign up and put your name in the lottery, as demand usually outstrips production.

 

Take your time selecting. Good luck. 

 

Bob

Edited by bobhen, 23 June 2022 - 02:25 PM.

[SilverLitz]

Here is my list of some good imaging refractors.  The SW Esprits are not quite as high quality as the rest.  I own an SVX130T, Esprit 100, and Vixen FL55ss, and I like them all, but the SVX130T is my favorite.  Each has different FL and FoV uses.  The table shows the FoV and image scale (measure of resolution) of each scope (w/ and w/o focal reducers; use field flattener w/o FR/FF) with various popular astrocams.  If you are wanting to image DSOs (which need many long exposures subs), I HIGHLY recommend plan on getting a dedicated, COOLED astrocam in the future, instead of using a DSLR.  Regulated cooling is very important.

 

You need to think about FoV and image scale and the targets you intend to image.  Your RC51 is a very specialized, very short FL OTA for the very largest targets.  The RC51 basically fits the need of my Vixen FL55ss, with FoV and image scales between the two that I have with my FL55ss.

 

My Esprit 100, especially reduced to 413mm @ f/4.13, fits the use case of the typical 80mm APO, but faster.  My decision on getting the Esprit 100, came down to between it and an SVX080-3SV, and I got a great deal on the Esprit and the SVX080 was backordered.  Since then prices have risen significantly, especially for the Chinese scopes.  Stellarvue's SVX series is much better than their older scopes with Chinese optics.  In today's environment, I really like the SVXs as they are of a quality similar the A-P (gold standard, w/ waits of many years), TEC, and Taks; actually how close is unknown as SV does not have the long track record of the others.  The difference is that SVXs are MUCH more available at more reasonable prices.  In today's market, I would probably pick the SVX080 or the just announced SVX090 over the Esprit.  My SVX130T is clearly a superior scope to my Esprit both optically and mechanically, but the Esprit was the bang/buck champ (though with prices up 30% in the past year, that is a tougher case now).  By all reports the current bang/buck champ is probably the AT92, 505mm @ f/5.5.

 

A scope in this above's 400-500mm FL and f/4 to f/6 would be my pick for your next scope, as there are MANY great targets that will fit, that your RC51 is just too short for.  Then after that, you can go for a 120-140mm f/7 OTA, but these will have greater demands, both in $$$$ and mount requirements.  My G11 handles my SVX130T fine, and I felt a 140mm was the most I would want to put on it for AP.  With your 811 mount, I would dial that back a bit.

 

Edited by SilverLitz, 23 June 2022 - 04:07 PM.

[ChuckS]

Here is my list of some good imaging refractors.  

Can I like this post twice? I saved this image and put in my now getting pretty big spreadsheet on astronomy. Thanks very much!

 

The SVX 102 is the scope that had captured my attention before I posted this and it's still strong.  It's a California company and they build them in-house - I sorta like the idea of my scope and mount being from Ca companies (living in Los Angeles).  Not that this really matters, but it does appeal to me. 

 

When I bought the GM811, I knew it might be a limiting factor - but you can upgrade the Dec drive (the RA is the same).  I expect it will take me a few years to tire of this next scope (and camera... my DSLR is not going to make the cut!).  Lot of targets for this focal length. 

[SilverLitz]

By all accounts, the SVX102T is a fine scope, and probably one of the best in the ~100/700mm range.  My hesitancy on the 102 vs. the 80/90 is that if you progress to an additional longer FL scope, the 102 would be redundant, while the shorter/faster 80/90 would not be.  My 1st scope was an ES ED102CF (714mm @ f/7), and I came to the opinion that its FL was a "tweener", e.g. too long for many targets, but too short for others.  I replaced the ED102CF with the Esprit 100, which is MASSIVELY better, optically/mechanically/practical FL.

 

In the year I have had my SVX130T, I have found that under the VAST majority of sky conditions, the SVX130T provides better resolution than my EdgeHD 925, suggesting that it may be as long as I will ever need.  The SVX130T gives me either 910mm @ f/7 or 680mm @ f/5.25, making it a much bigger workhorse than expected.  I expect SV's best AP scope is probably the SVX140T, which is very slightly longer/faster than my SVX130T.  I actually had bought a new SVX140T until last summer's shortage of FT focusers push out the deliver an extra 3 months, and I got the great opportunity to buy a nearly new SVX130T.

[Jon Isaacs]

Oh goodness we have seen it done and the results posted right here.  In the refractor forum no option is off the table.  GN

 

It can be done but it's not the right scope for the job. 

 

Jon

[ChuckS]

By all accounts, the SVX102T is a fine scope, and probably one of the best in the ~100/700mm range. My hesitancy on the 102 vs. the 80/90 is that if you progress to an additional longer FL scope, the 102 would be redundant, while the shorter/faster 80/90 would not be. My 1st scope was an ES ED102CF (714mm @ f/7), and I came to the opinion that its FL was a "tweener", e.g. too long for many targets, but too short for others. I replaced the ED102CF with the Esprit 100, which is MASSIVELY better, optically/mechanically/practical FL.

In the year I have had my SVX130T, I have found that under the VAST majority of sky conditions, the SVX130T provides better resolution than my EdgeHD 925, suggesting that it may be as long as I will ever need. The SVX130T gives me either 910mm @ f/7 or 680mm @ f/5.25, making it a much bigger workhorse than expected. I expect SV's best AP scope is probably the SVX140T, which is very slightly longer/faster than my SVX130T. I actually had bought a new SVX140T until last summer's shortage of FT focusers push out the deliver an extra 3 months, and I got the great opportunity to buy a nearly new SVX130T.

I was thinking 80/90 would be redundant to redcat 51…

[rgsalinger]

Nobody to my knowledge posts raw image files;

 

I did that twice in this thread and I have often posted links to full sized images on the cloud. I really don't see how you can recommend something to anyone for imaging when you don't supply some examples of the easily attained quality you can get with the telescope. 

 

It is, of course, useful to have a table like the one that was published by SilverLitz but the best way to provide information about an imagin scope is data as close to untouched as possible. 

 

Shopping by "brand" or "reputation" is, at leas to this consumer, comes in a poor second to actual actual images. In fact, when I recently had one of my scopes collimated, the vendor sent me exactly that - a set of 10 second exposures so that I could see what to expect from the scope. Odlly they had exactly the same camera that I had been using and getting poor results.

 

Rgrds-Ross 

[Oyaji]

Granted, Ross, that you kindly posted two raw image files.  But surely that is the exception and not the rule.  So maybe I should have said "Almost nobody to my knowledge posts raw image files."

 

Incidentally, one of the raw image files you posted had diffraction spikes.  (post no. 15).  Remind me not to buy that refractor!  

[Lagrange]

I've done very little astrophotography, just a few images in H-alpha, a few shots of the Moon, so I don't have much to add to that aspect of your question but I have been using TeleVue refractors for 25 years and have owned and looked through many other scopes over the years.

 

I know that it's very rare, even way out in Death Valley, to get an evening of "perfect" seeing. Processing can help select the best frames but can't improve seeing. So when we buy very high end telescopes we're buying something that we can only really use to it's full extent on certain nights when the seeing is very good, and we typically had to take a long drive to get to a dark site.

 

It's also true that an excellent all-around telescope like NP101 won't be the absolute best at everything. You could end up with many very expensive telescopes that are rarely ever used to their full capabilities.

 

Not knowing astrophotography very well at all, I'm going out on a limb here, but it seems you'd be wanting either wide field views or higher magnifications because there really aren't any telescopes that can deliver world-class performance for both.

 

100mm f7 is not a wide field telescope, but I'll speak to what I know. For larger Nebulae and star clusters I would think NP101is or NP127is with their great optics, focuser and OTA would be telescopes you could keep the rest of your life and be completely satisfied with. Takahashi is making a Petzval model that appears to be trying to compete with TeleVue https://optcorp.com/...g-ota-telescope.

 

Takahashi has been famous for making world class telescopes with a triplet lens assembly, and manufacturers don't always succeed when they try a new design so I would read all the reviews of the Takahashi Petzval before I'd buy one, but I'd be really surprised if they got it wrong.

 

In general, Astro Physics, TeleVue, Takahashi are brands people have trusted for decades. Those telescopes are keepers.

Tak have been making Petzvals for years and they're onto the second version (if I remember correctly) of the 106mm. There's no doubt of its capabilities either - Astrobin is absolutely full of incredible images taken with it. They even made a a 130mm f/5 for a while but that's very rare and expensive.

 

 

Well, the Hubble is an old design too!

It is, which is why space telescopes moved on to more advanced designs years ago but of course Hubble is still very capable in its own right.

 

Amateur scopes are generally nowhere near the cutting edge of optical design or manufacture and for very good reasons!

[rgsalinger]

Sorry about the mispost. This is actually the full frame from the 2500 dollar refractor. No flattener, just an IR/UV cut filter. Taken in Bortle 3 skies on a CEM120EC2 mount. I think that the quality versus price of this scope is hard to beat. As far as posting I often post raw images it's the only way to actually judge whether the quality is acceptable or not. 

 

 

 

That's not to say that looking at finished images on Astrobin is a waste of time, it certainly gives you an idea of what you can aspire to produce with a given set of components. 

 

Rgrds-Ross

[ChuckS]

Sorry about the mispost. This is actually the full frame from the 2500 dollar refractor. No flattener, just an IR/UV cut filter. Taken in Bortle 3 skies on a CEM120EC2 mount. I think that the quality versus price of this scope is hard to beat. As far as posting I often post raw images it's the only way to actually judge whether the quality is acceptable or not. 

 

ASKAR_full_frame.JPG

 

 

That's not to say that looking at finished images on Astrobin is a waste of time, it certainly gives you an idea of what you can aspire to produce with a given set of components. 

 

Rgrds-Ross

Ha, now here's the hard truth. I am such a rookie that I don't know how to evaluate what I am seeing in this image - whereas I understand a finished product. This trying to understand 'what next' is all based on my persistence in learning (which I am enjoying a lot) and the trajectory I am on, where I want to get to. As an avid golfer over many decades, I know it takes a while to understand complex things (eg., golf instruction which is somewhat analogous to astrophotography - lot of variables, plenty of subjectivity baked into it). So, in all likelihood I am going to rely on ppl's input to me. Plus what I can gather at places like Mt Pinos (where I am going tomorrow/Sat) where a lot of ppl are out. 

Edited by ChuckS, 23 June 2022 - 07:11 PM.

[james7ca]

There are a good number full-scale, "raw," or simply stretched images with FWHM (star size) and eccentricity (star roundness) measurements in a thread that I started on image quality back in 2015 with the most recent submissions done in 2021. There are images from quite a few of the major manufacturers (Tele Vue, A-P, Takahashi, Stellarvue).

 

However, it's a limited overview since only in a few cases are there more than one sample from a given scope. Nevertheless, it can be helpful in determining what to expect and as an aid in the evaluation of image quality.

 

Here is the link:

 

  https://www.cloudyni...y/#entry6627920

 

By the way, I would highly encourage those who have similar evaluations from their own scopes to post their results in this same thread (linked above). In the introduction I give an overview of what to post in terms of images and measurements so that the results are as similar as possible.

 

[begin]soapbox[/end]

On a similar quest, I would suggest that people try to refrain from posting screen shots of PixInsight's AberrationInspector results (or similar) since the on-screen scaling that MIGHT be applied during the capture of said screen could introduce distortions or pixelization in the posted result.

 

Unfortunately, I've seen similar problems in some of the posts in my thread on image quality and elsewhere on CN and what you need to do is to apply a simple histogram stretch to the raw image, run AberrationInspector to produce a 1200 x 1200 pixel result (since that is the largest square image that is allowed on CN), save that result at FULL resolution, and then post that image/file as an upload to CN. Obviously, if you don't have PixInsight you can do something similar by just taking appropriately sized crops from the corners, sides, and center of your image. The key points being that you do NOT want to introduce any scaling from the original capture and you need to sample from all four corners and edges and from the center of the image.

 

The same is true if you want to post an enlarged image, don't scale the image on screen and then do a simple screen shot. Rather, use a proper rescaling algorithm, save that result and then post the file.

[begin]off of the soapbox[/end]

[ChuckS]

I bought an ASKAR 107PHQ for 2500USD. Here's a blown up screen shot of an QHY268 APS-C using Aberration Inspector in Pixinsight. This is a 4" F 7.5 telescope and, as you can see is a superb performer. Unless you really feel that you can't get a nice picture in one night with this scope, I would strongly recommend it over the more expensive brands. With the advent of the high QE back illuminated Sony chips, you really don't need an F 5 telescope to come home with a very nice picture. 

 

askar.JPG

 

Here's an example of what I was abble to craft with 8 hours of integration time using that very scope. 

 

Here's an example using the scope with less than 4 hours of integration time. 

 

 

I think that people are still unaware that the Chinese telescope makers have come a long way in terms of quality offerings at lower prices. I'm just hoping that they come up with an equivalent wide field telescope sometime soon. 

 

Of course an AP, Tak, TV and maybe even the latest SV scopes have better mechanics but if you don't want to spend that kind of money, these new ASKAR scopes are just wonderful. 

 

Rgrds-Ross

Going back thru all the posts in detail. Interesting. Absolutely now on the list for full scrutiny. Thanks for all your input on this (and on cameras elsewhere)

[ChuckS]

Stellarvue SVX102T. Highest quality APO triplet 102mm F7. Produced right here in the USA.

 

https://www.stellarvue.com/svx102t/

 

Give them a call and talk to them. They offer fantastic personal service both before and after the sale.

They are (relatively speaking) just up the road for me here in Los Angeles. I saw a youtube video last night that went thru their shop, and of course I don't know enough to be a critical vuer of this, but regardless, I was impressed.

[SilverLitz]

I was thinking 80/90 would be redundant to redcat 51…

I would agree that 102mm, f/7 would be meaningful addition to RC if that would be the extent of you longer FL, but 120-140mm gives you meaningfully more useful FL.  If you had RC51 + 130mm, you would prefer the 3rd scope to be the 80/90mm instead of 102mm.  If you were only going to have 2 scopes, RC51 would be better w/ 102mm than 80/90mm.

 

FoV of RC51 on 268 (APS-C):  323'x215' w/ 3.1"/px image scale; very large FoV and low resolution (lower res on you Nikon, larger pixels)

this is very nice for the very large: Cygnus Loop (both East/West), Heart+Soul, North America+Pelican, & Question Mark

 

From my table:

130mm @ f/7:    88'x59'; 118'x79' (w/ FR)

102mm @ f/7:  113'x75';  151'x101' (w/ FR)

80mm @ f/6:    168'x112'; 210'x140' (w/ FR)

 

Look at your target lists, and see what fits the best w/ your camera options.

 

For me, I find my Esprit 100 @ 413mm, is a much better middle scope between my Vixen FL55ss and SVX130T, than a 102mm/714mm scope.  Again the Esprit 100 has a FoV more like the 80/90 than the 102.

[rgsalinger]

The screen shots that I posted look identical on my display at home. The reason I posted those is simply to point out the fact that reputation is not everything. New things, techniques and materials come along all the time. It's worth looking at some outliers from time to time if there's a compelling reason to do so.

 

I am certain that there are even better shots that could be posted of much more expensive gear and who knows how long my ASKAR will last. It might turn to dust. 

 

Here's a link to another random 300 sec image taken the same night in the same conditions https://drive.google...iew?usp=sharing . 

 

Rgrds-Ross

[ChuckS]

I would agree that 102mm, f/7 would be meaningful addition to RC if that would be the extent of you longer FL, but 120-140mm gives you meaningfully more useful FL.  If you had RC51 + 130mm, you would prefer the 3rd scope to be the 80/90mm instead of 102mm.  If you were only going to have 2 scopes, RC51 would be better w/ 102mm than 80/90mm.

 

FoV of RC51 on 268 (APS-C):  323'x215' w/ 3.1"/px image scale; very large FoV and low resolution (lower res on you Nikon, larger pixels)

this is very nice for the very large: Cygnus Loop (both East/West), Heart+Soul, North America+Pelican, & Question Mark

 

From my table:

130mm @ f/7:    88'x59'; 118'x79' (w/ FR)

102mm @ f/7:  113'x75';  151'x101' (w/ FR)

80mm @ f/6:    168'x112'; 210'x140' (w/ FR)

 

Look at your target lists, and see what fits the best w/ your camera options.

 

For me, I find my Esprit 100 @ 413mm, is a much better middle scope between my Vixen FL55ss and SVX130T, than a 102mm/714mm scope.  Again the Esprit 100 has a FoV more like the 80/90 than the 102.

I thought I was doing well to consider how a new scope meshes with a new camera. You just took it to the 3rd scope! And we all know, there will be a 3rd scope. 

 

Here's how I think about targets - first, nebulae, galaxies & clusters. Second, moon. Planets are a distant 3rd.  But with nebulae, galaxies and clusters, I like as much resolution as I can get while still getting a sense that these objects are out there in the vastness of space.  Especially some images I see of nebulae fill the frame to the point that I feel claustrophobic.  I am not sure how this maps to a 3 telescope strategy, but that's the best I can do. 

 

I was thinking with a little slower 100mm I'd add a reducer to provide 2 focal lengths with one scope.  

[peleuba]

I am about 8 months into astrophotography (with no background in astronomy prior) and have made progress. My current rig is Losmandy GM811G, Redcat 51, and Nikon modded DSLR.  I am learning PixInsight and NINA. Definitely, my skills are improving. I am now starting to think about a longer focal length refractor - probably in the 100mm, f/7 range. I want something that will be a long-term keeper. I have been shooting mainly nebulae, galaxies and star clusters, and these will remain my primary targets for the foreseeable future.

 

 

Lots of good information from lots of experienced folk.  

 

This will go against the grain, but its true.  You do not need a super high Strehl and low PtV lens to take good astrophotos.  This is an absolute truism.  Flat field, good mount/tracking and image processing will MORE then makeup for any sins in the Strehl or PtV.    

 

Yes larger means higher resolution.

 

Reducers "reduce" the focal ratio of the scope allowing you to gather data quicker.

 

Flatteners "flatten" the field so that stars look natural.

 

Now for some editorial comments.  I find it a bit sad, that you've not spent some serious eyepiece time behind a scope.  Its hard to understand what a telescope can do if you've not used it visually, at least a little bit. 

 

Using a scope visually will make you a better astrophotographer.  

[ChuckS]

Lots of good information from lots of experienced folk.  

 

This will go against the grain, but its true.  You do not need a super high Strehl and low PtV lens to take good astrophotos.  This is an absolute truism.  Flat field, good mount/tracking and image processing will MORE then makeup for any sins in the Strehl or PtV.    

 

Yes larger means higher resolution.

 

Reducers "reduce" the focal ratio of the scope allowing you to gather data quicker.

 

Flatteners "flatten" the field so that stars look natural.

 

Now for some editorial comments.  I find it a bit sad, that you've not spent some serious eyepiece time behind a scope.  Its hard to understand what a telescope can do if you've not used it visually, at least a little bit. 

 

Using a scope visually will make you a better astrophotographer.  

Paul, every time I look thru a telescope, I feel like I am really missing something by being so astrophotography fixed. 

 

I don't know if you can get one OTA that you can use for both. I think I recall that you can't do both at the same time, but I think with some you must be able to swap out eyepiece for camera thru some means or another. I'd like that. As I learn and get a little more advanced, the computer becomes more central, and instead of looking at the sky I am looking at a screen. NOT my goal. 

[james7ca]

<snip>...

This will go against the grain, but its true.  You do not need a super high Strehl and low PtV lens to take good astrophotos.  This is an absolute truism.  Flat field, good mount/tracking and image processing will MORE then makeup for any sins in the Strehl or PtV. ...<snip>

I really can't agree with that statement (as an "absolute truism"). Perhaps in the days of film-based imaging or the early days of digital when people were using CCD cameras with huge pixels such a claim might have been somewhat true. But, we are well beyond that today with our small-pixel CMOS cameras that allow short exposure, low-read-noise imaging. It really depends upon a number of factors and while you can take astrophotos with just about anything that doesn't mean you're going to get really good results with just any telescope.

 

For astrophotography you need very good color correction (better than for visual work), a flat field (flatter than you need for visual work), round and well-shaped stars (probably more so than for visual unless you like to study stars at very high magnifications), and decent resolution (here the differences between the requirements for visual and photography probably converge, but in most cases the better the optics the better the image).

 

Many visual observers are probably completely happy with "fast" doublet achromats for wide-field viewing or "long" f/10 doublets for planetary or double star work. So, that's probably telling you something about the relative comparisons between visual and imaging since neither of those kinds of scopes would make a good astrograph (although either COULD be used for imaging and I have an inexpensive  4" f/10 achromat that I've used for solar and lunar imaging, examples __HERE__ and __HERE__ on CN).

 

All that said, the end user makes a huge difference in all of this, since a poor astrophotograher can take bad pictures with the best of equipment while a really good one can probably produce very nice results with only modest equipment. But, in either case a better scope makes it easier to get good results.