62 replies to this topic

[EPinNC]

I've been using this setup for a while now:

• iOptron CEM26 mount
• Nikon DSLR camera (D7000 at first, now a D5600)
• Orion Apex 102mm f/12.7 Mak-Cass (1300mm focal length) telescope

I like the "reach" of the Mak-Cass, but it's just too much focal length.  So, I'm looking to get a shorter focal length refractor with a wider field of view.

 

I'm keeping the mount and camera for the foreseeable future, so I'm not interested in replacing those.

 

As this album suggests, I've had some success with my Mak-Cass, but it's been too much work.  I'm interested mainly in open/globular clusters, broad-spectrum nebulae, and a few of the brighter galaxies such as M51, M81/82, M104, NGC 7331, etc.  I'm not trying for HII emission regions, so I'm leaving the DSLR unmodified.  Small planetary nebulae and tiny galaxies are, of course, not on the list of expectations.

 

Let's say the budget is $500-1000 US, although closer to the lower end is preferable.

 

Two possibilities that come to mind:

 

The Astro-Tech AT102ED seems interesting for its focal length (714mm), which is more forgiving than my Mak-Cass yet still has some reach.  The price is nice, too.  But I'm a little worried about (1) its physical size relative to the CEM26, (2) the fact that it's a doublet and might be prone to star halos, and (3) it would require a flattener, which is more length and possible issues with flex and backfocus.

 

The Astro-Tech AT80EDT is also interesting because I assume that, it being a triplet, I would not need a flattener.  (Is that correct?)  However, it's only 480mm focal length.

 

The SVBONY SV550 80mm triplet looks similar to the AT80EDT.

 

In terms of the field of view, the astronomy.tools FOV calculator shows the following on Messier 13 3 (one of the smaller globulars):

 

• red = current 1300mm f/12.7 (Mak-Cass)
• green = 714mm f/7 (i.e., AT102ED)
• cyan = 480mm f/6 (i.e., AT80EDT or SV550)

Seeing conditions in my Bortle 7 suburban habitat are not particularly good.  So, my Mak-Cass makes for fuzzy stars, as you can see in my album linked above.  So I'm not really getting any benefit from the narrow field of view.  (And of course the mount won't track well enough anyway.)

 

In terms of pixels, astronomy.tools CCD suitability calculator shows my current setup to be oversampled, but the other focal lengths seem to be reasonably good in either "OK" or "Poor" seeing.

 

Would the 80mm triplets still resolve globular clusters to their core using my D5600 (assuming decent seeing)?  If such objects are small but still nice and sharp using my D5600, I'd be pleased.

 

What important considerations have I left out?

Edited by EPinNC, 04 February 2023 - 04:13 PM.

[matt_astro_tx]

Triplets still need flatteners.  It's petzvals that don't.  I'd go AT over Svbony.  I would also go triplet over a doublet to minimize/avoid CA.

Edited by matt_astro_tx, 04 February 2023 - 05:06 PM.

[jimhoward999]

You still need a flattener with a triplet.  You have to go to Petval/quad design to avoid the flattener. 

[Achernar]

I've been using this setup for a while now:

• iOptron CEM26 mount
• Nikon DSLR camera (D7000 at first, now a D5600)
• Orion Apex 102mm f/12.7 Mak-Cass (1300mm focal length) telescope

I like the "reach" of the Mak-Cass, but it's just too much focal length.  So, I'm looking to get a shorter focal length refractor with a wider field of view.

 

I'm keeping the mount and camera for the foreseeable future, so I'm not interested in replacing those.

 

As this album suggests, I've had some success with my Mak-Cass, but it's been too much work.  I'm interested mainly in open/globular clusters, broad-spectrum nebulae, and a few of the brighter galaxies such as M51, M81/82, M104, NGC 7331, etc.  I'm not trying for HII emission regions, so I'm leaving the DSLR unmodified.  Small planetary nebulae and tiny galaxies are, of course, not on the list of expectations.

 

Let's say the budget is $500-1000 US, although closer to the lower end is preferable.

 

Two possibilities that come to mind:

 

The Astro-Tech AT102ED seems interesting for its focal length (714mm), which is more forgiving than my Mak-Cass yet still has some reach.  The price is nice, too.  But I'm a little worried about (1) its physical size relative to the CEM26, (2) the fact that it's a doublet and might be prone to star halos, and (3) it would require a flattener, which is more length and possible issues with flex and backfocus.

 

The Astro-Tech AT80EDT is also interesting because I assume that, it being a triplet, I would not need a flattener.  (Is that correct?)  However, it's only 480mm focal length.

 

The SVBONY SV550 80mm triplet looks similar to the AT80EDT.

 

In terms of the field of view, the astronomy.tools FOV calculator shows the following on Messier 13 3 (one of the smaller globulars):

 

astronomy.tools-FOV-calculator.jpg

• red = current 1300mm f/12.7 (Mak-Cass)
• green = 714mm f/7 (i.e., AT102ED)
• cyan = 480mm f/6 (i.e., AT80EDT or SV550)

Seeing conditions in my Bortle 7 suburban habitat are not particularly good.  So, my Mak-Cass makes for fuzzy stars, as you can see in my album linked above.  So I'm not really getting any benefit from the narrow field of view.  (And of course the mount won't track well enough anyway.)

 

In terms of pixels, astronomy.tools CCD suitability calculator shows my current setup to be oversampled, but the other focal lengths seem to be reasonably good in either "OK" or "Poor" seeing.

 

Would the 80mm triplets still resolve globular clusters to their core using my D5600 (assuming decent seeing)?  If such objects are small but still nice and sharp using my D5600, I'd be pleased.

 

What important considerations have I left out?

I have an Astro-Tech 80mm EDT refractor, and it's an excellent visual and imaging telescope. However, you will want the field flattener and focal reducer. The camera rotator and eyepiece holder unscrew from the draw tube and the focal reducer and field flattener is screwed into it's place. However, this telescope is for quite large objects, much larger than most if not all globular clusters. It's mainly best for comets, large nebulae and star clusters and a few of the largest in apparent size galaxies. Triplets are better at suppressing those blue haloes around stars than doublets, so you'll want a triplet. I would choose a 120mm triplet for galaxies and globular clusters over the A-T 80mm EDT. Better scale up your mount accordingly.

 

Taras

Edited by Achernar, 04 February 2023 - 05:37 PM.

[Robert7980]

Under a thousand I would say there is only one, SV550 w flattener and rotator... Comes in right at 1k.... I'm pretty happy with mine, pretty tack sharp to almost medium format, easily covers full frame flat... Zero chromatic aberration, my copy doesn't like the cold though has some pinched optics when the rig is covered in ice... pretty killer for the money I think though...   

 

Here are some images from it, my skills aren't great, I'm still learning how to use this rig, so overlook most of the problems, those are caused by me not the scope... 

 

https://www.astrobin.../users/Rob7980/

[EPinNC]

Under a thousand I would say there is only one, SV550 w flattener and rotator... Comes in right at 1k.... I'm pretty happy with mine, pretty tack sharp to almost medium format, easily covers full frame flat... Zero chromatic aberration, my copy doesn't like the cold though has some pinched optics when the rig is covered in ice... pretty killer for the money I think though...   

 

Here are some images from it, my skills aren't great, I'm still learning how to use this rig, so overlook most of the problems, those are caused by me not the scope... 

 

https://www.astrobin.../users/Rob7980/

Wow, those are some really nice images!  The SV550 images are all at native focal length?  That NGC 2403 image is especially interesting because of all those little galaxies in the background -- even some of those show structural detail.

 

I seem to be making a beginner's mistake in thinking that short FL and wider FOV automatically equate to less "detail".  Clearly a wider scope can have good resolution if it's paired with an appropriate camera and good seeing.  I doubt that a Nikon D5600 would match an ASI2600MM astrocam, but this makes me optimistic that I might actually get better images from a shorter and faster scope.

[EPinNC]

I have an Astro-Tech 80mm EDT refractor, and it's an excellent visual and imaging telescope. However, you will want the field flattener and focal reducer. The camera rotator and eyepiece holder unscrew from the draw tube and the focal reducer and field flattener is screwed into it's place. However, this telescope is for quite large objects, much larger than most if not all globular clusters. It's mainly best for comets, large nebulae and star clusters and a few of the largest in apparent size galaxies. Triplets are better at suppressing those blue haloes around stars than doublets, so you'll want a triplet. I would choose a 120mm triplet for galaxies and globular clusters over the A-T 80mm EDT. Better scale up your mount accordingly.

 

Taras

Hm.  If I use a reducer on a 480mm f/6 scope, would that not make small things even smaller, possibly down to the point of undersampling?

 

I fully admit that there are many, many things about this of which I am totally ignorant!

[Spaceman 56]

 

Let's say the budget is $500-1000 US, although closer to the lower end is preferable.

 

don't look past the Stellarvue SV80A doublet.

 

very happy with mine. 

[EPinNC]

don't look past the Stellarvue SV80A doublet.

 

very happy with mine. 

Ah, I was waiting for you for chime in   I knew you have some kind of small refractor but I couldn't remember what it was.

 

It doesn't look like that particular one is available new anymore.  Some on the used market, but I'm a bit hesitant to go there.  The others available new are way out of my budget range.

 

I'm definitely open to other brands and models...  Thanks for the ideas!

[Spaceman 56]

Ah, I was waiting for you for chime in   I knew you have some kind of small refractor but I couldn't remember what it was.

 

It doesn't look like that particular one is available new anymore.  Some on the used market, but I'm a bit hesitant to go there.  T

I got mine second hand from CN classifieds for $600.  

 

there was one on CN recently for $500 with a focal reducer as well. 

 

but I checked when I looked at your post and I think its gone. 

[Robert7980]

Wow, those are some really nice images!  The SV550 images are all at native focal length?  That NGC 2403 image is especially interesting because of all those little galaxies in the background -- even some of those show structural detail.

 

I seem to be making a beginner's mistake in thinking that short FL and wider FOV automatically equate to less "detail".  Clearly a wider scope can have good resolution if it's paired with an appropriate camera and good seeing.  I doubt that a Nikon D5600 would match an ASI2600MM astrocam, but this makes me optimistic that I might actually get better images from a shorter and 

Small wide feild refactors have the most detail of any scope, that’s just physics.. There’s no center obstruction as mirror tube have, As refactors get larger they are still very good, but the law of physics start reducing what glass can do… So small (6” or less APO refactors are the top of the tack sharp designs… The SV550 isn’t the best scope on the market, it’s just one of the best at the lowest price point, I would say SVBoney is selling it underpriced, I would have paid more for it…

 

Everything I’ve shot so far was native 483mm f/6 with the 1 to 1 feild corrector… It’s a nice scope, it’s extremely well made has a nice focuser, all high quality machined metal and heavy… The optics are clear to 68mm and the corrector is also exactly the same size as a 12oz soda can, so it’s huge, easily handles full frame… The only thing I didn’t like about it was the rail, it works fine, same rail that’s on most other scopes, but it was too close and short for what I needed so I put it on a Losmandy plate I got from Farpoint with some risers for around a hundred bucks, that fixed everything I didn’t like about it… now I can mount this under it, in fact everything… the mini PC and power distribution will go under it when I have time to finish it… 

 

A DSLR would be fine on it, that’s what I started with, it’ll do everything the 2600MM will do it just takes a little more work and your calibration has to be good, so a DSLR is not as much of a limit as you think… Cooled cameras have a little better performance, but mostly they are just easier, you can shoot much longer frames with them without building up noise, THAT is the only thing they do that your DSLR can’t, if you’re shooting 30 or 60 second subs then you don’t really need the cooling…  The cooled cameras will let you go for 10 minutes or more… So that’s the difference… For narrowband this comes in handy because the shots can go 800 seconds or longer… 

 

I’m by no means telling you what to buy, there are other good choices, all I can do is say I’ve got something that meets most of your specs and I’m happy with it… it’s not perfect, but it also wasn’t $8,000 so I’ll live with the small flaws… You can see from the images what it does and my skills aren’t that good (I’m beginner-intermediate not expert) so the tube is still better than I am, the images are limited by me not the gear… For a stater scope that’s not a toy and isn’t crazy expensive I’d say it fits the bill… I’ll eventually add more optics, right now I’m still dialing in the 80 and the Samyang 135 wide feild… So few clear nights this winter that’s taking longer than expected… But that’s ok, it’s not a race… 

 

Edited by Robert7980, 05 February 2023 - 07:11 AM.

[mayhem13]

The AT80edt and SV550 are the same scope with different color schemes. Whichever of the two is more accessible is the one to choose. I purchase from our host Astronomics whenever possible.

 

There’s a new scope on the horizon coming from Astro Tech that has a bit more focal length, the AT90cft. It’s outside of your budget cap but given the specs and your intended targets I think it would be worth the stretch and your consideration. Either scope will work well with your mount and camera.

Edited by mayhem13, 05 February 2023 - 08:17 AM.

[EPinNC]

Thank you everyone for all your comments!  They have all been very helpful, especially the detailed discussion by Robert7980.  (Thanks so much for all that!)

 

While this purchase is still a couple of months over the horizon, I'm starting to lean towards one of the 80mm triplets.  I too would prefer purchasing from Astronomics if possible -- great service!

 

Optically, the two scopes do look essentially the same, with the differences mainly in accessories and attachments.

 

At the risk of being pesky, I have additional questions:

 

(1)  First,

 

I'd go AT over Svbony.

 

What specifically would you say makes you lean toward A-T vs. Svbony?

 

(2)  I like the fact that Svbony's field flattener is clearly specific to the SV550.  How specific is the A-T field flattener to the AT80EDT?

 

(3)  I still don't quite understand the components of flatteners and spacing.  From what I can tell, it appears that:

 

(a)  the flattener itself inserts into the telescope focusing tube;

 

(b)  the flattener accepts either a threaded T-ring or an extension tube;

 

©  the extension tube is optional.

 

Is that correct?

 

The A-T flattener's description says "Optimal spacing from the shoulder of the field flattener (where a T-ring threads on) to a camera's imaging sensor or film plane is 57mm +/- 4mm."

 

The Nikon D5600 F-mount has a "flange focal distance" of 46.5mm according to this source (which mirrors the Nikon F-mount Wikipedia page).  I currently have this T-ring with M42 (42mm x 0.75) threads and a thickness of 8mm.  The total distance would thus be 46.5 + 8 = 54.5mm.  Could I use just the flattener itself and my existing T-ring, without the extension tube?  Or would I need a different size T-ring with different threads?  Where does the extension tube fit into this?

 

(3)  I like the longer Vixen rail on the SV550.  Balance could be a significant issue with a DSLR, especially when adding a field flattener on my CEM26 mount, which has a very back-set DEC axis position.  Could the rail that comes with the AT80EDT be reversed or repositioned?  I do have another, rather long rail that came with the CEM26 -- I might be able to substitute that, assuming the screws/holes match well.

 

(4)  The AT80EDT is described as having "A built-in camera angle adjuster" (rotator), while the SV550 does not and would need to be a separate purchase.  I like to shoot with celestial north to the "top" of the image frame (as the camera is typically held in hand), although occasionally I might want to rotate it 90 degrees.  If I got the SV550, would I actually need a camera rotator?  Could I not just rotate the whole telescope in the tube rings?  I know this might affect balance slightly, and I suspect the reason that might not work for some setups is if there were other components attached to the tube (e.g., guide scope).

 

Again, I appreciate your patience in wading through all my questions!  Thank you very much for any and all insights or suggestions!

[matt_astro_tx]

What specifically would you say makes you lean toward A-T vs. Svbony?

Primarily that its sold by Astronomics, a small family-owned business in the USA.  Exceptional customer support, delivery speed, and reputation.

 

I have also heard that Mike requires certain quality specs of the manufacturer (for example strehl ratio) and we don't know if Svbony does the same.  (They might... I don't know.)

 

Lastly, I own an AT scope and plan to buy another.  I also own some Svbony gear (accessories and a guidescope).

Edited by matt_astro_tx, 05 February 2023 - 03:44 PM.

[Spaceman 56]

 I'm starting to lean towards one of the 80mm triplets. 

I think one of the questions to ask is are you going to stay with OSC or move to Mono ?

 

Triplets are much more expensive than Doublets, and perhaps that matters when shooting OSC.

 

I have noticed some people shoot Mono with Doublets, and use large aperture ones. the CA won't matter so much if you shoot in Mono with filters.

 

Actually someone said the cost of 2 inch filters (for mono) was offset by not having to spend more on the Triplet.

[EPinNC]

I think one of the questions to ask is are you going to stay with OSC or move to Mono ?

 

Triplets are much more expensive than Doublets, and perhaps that matters when shooting OSC.

 

I have noticed some people shoot Mono with Doublets, and use large aperture ones. the CA won't matter so much if you shoot in Mono with filters.

 

Actually someone said the cost of 2 inch filters (for mono) was offset by not having to spend more on the Triplet.

I don't see myself going to that level of sophistication in the next several years.  I've seen discussion of using a doublet and handling the seemingly-common chromatic abberation with mono, and I worry that OSC on a doublet will pick up too much of that.  That's why I'm thinking of a triplet, despite the cost.  For the next few years, I just want to focus on getting really nice broad-spectrum subjects with a simple-but-good-quality setup.

 

Thanks for the thoughts!

 

I'd love to get your thoughts on some of my other questions, since you seem to already have experience in setting up a very similar system

[matt_astro_tx]

Absolutely recommend a triplet for broadband OSC.  You will get CA with a doublet.  For example, I have an FPL-53/Lanthanum doublet.  Arguably supposed to be the best lens materials for reducing CA, and yet I still have noticeable CA in my OSC images.  The image below shows my struggle.   

The R,G channels are tack sharp, while the B channel is just a bunch of blobs.  Note that I use an EAF.

 

 

This was taken with my AT60ED and ASI183MC Pro with a UV/IR Cut Filter.

[Spaceman 56]

CA.  I worry that OSC on a doublet will pick up too much of that.  That's why I'm thinking of a triplet, despite the cost. 

thats the general consensus of opinion, but for my own personal experience I have not experienced that problem at all. 

 

perhaps my Stellarvue is better than the average doublet (someone said that in another thread) or perhaps its my B1 location.

 

for myself for wide field, and low F Ratio, i am happy with the doublet. check out my gallery if you are uncertain.

[Spaceman 56]

 

Absolutely recommend a triplet for broadband OSC.  You will get CA with a doublet.  For example, I have an FPL-53/Lanthanum doublet.  Arguably supposed to be the best lens materials for reducing CA, and yet I still have noticeable CA in my OSC images.  The image below shows my struggle.   

The R,G channels are tack sharp, while the B channel is just a bunch of blobs.  Note that I use an EAF

 

This was taken with my AT60ED and ASI183MC Pro with a UV/IR Cut Filter.

 

Matts info is good. 

 

and we are both just being honest. 

[matt_astro_tx]

I should note that CA like mine can easily be processed out, and a great many folks who I've given my raw stacks too don't have a problem doing so.  I'd however prefer not to have to deal with it, so my next scope will be a triplet.

[imtl]

Small wide feild refactors have the most detail of any scope, that’s just physics.. There’s no center obstruction as mirror tube have, As refactors get larger they are still very good, but the law of physics start reducing what glass can do… So small (6” or less APO refactors are the top of the tack sharp designs… The SV550 isn’t the best scope on the market, it’s just one of the best at the lowest price point, I would say SVBoney is selling it underpriced, I would have paid more for it…

 

Everything I’ve shot so far was native 483mm f/6 with the 1 to 1 feild corrector… It’s a nice scope, it’s extremely well made has a nice focuser, all high quality machined metal and heavy… The optics are clear to 68mm and the corrector is also exactly the same size as a 12oz soda can, so it’s huge, easily handles full frame… The only thing I didn’t like about it was the rail, it works fine, same rail that’s on most other scopes, but it was too close and short for what I needed so I put it on a Losmandy plate I got from Farpoint with some risers for around a hundred bucks, that fixed everything I didn’t like about it… now I can mount this under it, in fact everything… the mini PC and power distribution will go under it when I have time to finish it… 

 

A DSLR would be fine on it, that’s what I started with, it’ll do everything the 2600MM will do it just takes a little more work and your calibration has to be good, so a DSLR is not as much of a limit as you think… Cooled cameras have a little better performance, but mostly they are just easier, you can shoot much longer frames with them without building up noise, THAT is the only thing they do that your DSLR can’t, if you’re shooting 30 or 60 second subs then you don’t really need the cooling…  The cooled cameras will let you go for 10 minutes or more… So that’s the difference… For narrowband this comes in handy because the shots can go 800 seconds or longer… 

 

I’m by no means telling you what to buy, there are other good choices, all I can do is say I’ve got something that meets most of your specs and I’m happy with it… it’s not perfect, but it also wasn’t $8,000 so I’ll live with the small flaws… You can see from the images what it does and my skills aren’t that good (I’m beginner-intermediate not expert) so the tube is still better than I am, the images are limited by me not the gear… For a stater scope that’s not a toy and isn’t crazy expensive I’d say it fits the bill… I’ll eventually add more optics, right now I’m still dialing in the 80 and the Samyang 135 wide feild… So few clear nights this winter that’s taking longer than expected… But that’s ok, it’s not a race… 

 

 

You stated it can easily handle FF. Have you tested it on a FF? 

 

Are the images you posted on Abin cropped? Is there an option to see a raw unprocessed sub out of your 2600?

[Spaceman 56]

  I'm interested mainly in open/globular clusters, broad-spectrum nebulae, and a few of the brighter galaxies such as M51, M81/82, M104, NGC 7331, etc.  I'm not trying for HII emission regions, so I'm leaving the DSLR unmodified.  Small planetary nebulae and tiny galaxies are, of course, not on the list of expectations.

 

Seeing conditions in my Bortle 7 suburban habitat are not particularly good. 

 

Would the 80mm triplets still resolve globular clusters to their core using my D5600 (assuming decent seeing)?  If such objects are small but still nice and sharp using my D5600, I'd be pleased.

 

Hi EPinNC. I went back to your original post to remind myself what we are talking about.

 

answers. expressed in relationship to my experience with an 80mm Stellarvue Doublet.

 

1. Globular clusters are bright. easy to shoot and get reasonable results. both these were DSLR shots with the same DSLR you use (Nikon D5600)

 

Click to enlarge.

 

 

 

Galaxies are harder with an 80mm, because the focal lengths a bit lacking. I don't shoot galaxies because of this.

 

got this shot of Markarians Chain. 

 

Click to enlarge.

 

 

for wide field Nebulae I think the 80mm refractor is a good choice. 

 

click to enlarge.

 

 

 

 

maybe these shots give an indication of whats possible with an 80mm.

 

if this is the type of FOV and focal length you require, or that appeals to you, then I guess the question is how good an 80mm can you afford.

 

if you can afford a triplet, then I would look for an 80mm  Stellarvue Triplet, as I totally trust in the Stellarvue quality. look what the big ones cost.

 

Hope this all helps somehow EPinNC. 

 

 

 

 

 

 

 

[EPinNC]

The main problem I'm trying to solve is the great difficulty in using a very long focal length for the quality of my mount.  Good as it is, there's really only so much you can ask of a CEM26, and a 1300mm scope is asking too much.  As for why I chose the 1300mm Mak in the first place...  small, light, and inexpensive.  Other than that, I really didn't know what I was getting into.  I've done the best I can reasonably do, but it's really time to take a more sensible approach.

 

So, I'd like to back off to something that makes the whole image-making process simpler and more rewarding.

 

There are also objects that I can't even fit in the FOV (e.g., Pleiades).

 

From all the examples I've seen, I have room to use a smaller, wider-FOV refractor and still get sharp images of somewhat smaller objects.

 

I don't have a lot of money, so the AT102ED seemed appealing -- a good telescope that is still a decent focal length without breaking the bank, one that is still a not unreasonable size for my CEM26, and one that should give me less frustration.

 

However, doublets in my price range seem prone to chromatic aberration (vendor claims notwithstanding) and, to quote matt_astro_tx:

 

I'd however prefer not to have to deal with it...

Clearly, there are some 80mm f/6 triplets that cost only a little more and give images that are mostly better than mine.  See examples from Robert7980 and Spaceman 56.  Cropped or not, those images are *still* notably better than mine.

 

I don't suppose there's a good 700mm triplet for less than $1000 US, including field flattener, is there?

[lancing]

The Svbony SV550 or the AT80EDT are very similar scopes. I've not heard of any optical performance difference between the two.

 

My national telescope retailer here in Canada has started stocking the Svbony SV550 and they keep selling out every time they get a shipment. The Svbony SV550 is using FPL51​, the AT80EDT is using either FPL-51 or something equivalent as well.

 

It has no CA at all. The flattener for the SV550 works well and has a spot to mount a 2 inch filter. You basically remove the 2" interface connector the scope comes with and replace it with the SV210 rotator which is threaded for M63, then screw in the SV209 flattener and extension tube onto it which is threaded for M63 at the front and either M63 or M48 at the back.

 

I've not heard any complaints about the AT80EDT either so I'd just go with whichever option is easier for you to purchase.

 

I would definitely not recommend 1300mm focal length for a beginner. It can be done but you are going to crank up the difficulty a bit.

Edited by lancing, 05 February 2023 - 09:19 PM.

[Rafael Amarins]

As an OSC user coming from a 72ED F6 Doublet to a 102 Triplet I noticed a significant improvement in sharpness in stars. Both OTAs made by the same manufacturer. 

I use a CEM25 btw. This OTA is the biggest my mount would handle with no issues (14lbs total). 

Unless you plan on using this mak for lunar, planetary and planetary nebula once you buy the refractor you'll never use it again. 

SV550 and AT80EDT are the same scope basically. Maybe AT has a better quality control so it's up to you. 

There is a reason triplets are much more expensive than doublets. Unless you're planning to use mono/narrowband (if you're lazy and cheap like me considering all the gear and work required to capture mono) you should by a triplet. 

Under 1k there is no better option than a 80mm triplet IMO