15 replies to this topic

[Ritaelyn]

I fell in love with doing astrophotography by doing short exposure imaging on my 12" newtonian dobsonian mounted telescope. I've been doing this since November. I'm considering buying a 12" F4 ONTC Newtonian reflector + an equitorial mount for it. How well does the ONTC Newtonians work with a full frame (IMX455) setup such as with the ASI6200MM or Player One Zeus 455M Pro, assuming it has the proper 100mm secondary mirror? 

 

I'm also on the fence of sending it to a remote observatory like Starfront, vs keeping it here with me. I live in bortle 8 skies, but I have access to bortle 4.5 - 5 within 60 minutes, and bortle 1 within 2.5 hours. I'm only able to visit bortle 1 areas I'd say once every 2 months - possibly once every month. I know 1 hour in bortle 1 = 45 hours in my bortle 8 skies.

 

My desires are doing medium-field mosiacs astrophotography of deep space objects - nebulas like m42, m45, galaxies such as m31, leo triplet (m65, m66), other nearer galaxies, etc. I want to shoot in LRGB + SHO. I'm willing to budget up to $20k for the entire system - OTA, mount, and filters. The ONTC weighs 17kg (37lbs) and my imaging equipment weighs 7 lbs, for 44 lbs total mount weight. I'd likely throw it on a CEM70 if I travel with it. If I go remote I might try the CEM70, but I'd be prepared to buy a CEM120 for it given it might act like a wind sail. Given my experiences with short exposure photography on the dob - I don't mind seeing if I can write code or a plugin to switch to short exposures if wind > X mph in NINA.   

 

I made a spreadsheet of a list of all the targets I could think of so far and an APS-C camera spat out a 2x3 panel (6 panels) for andromeda, while a full frame sensor could do it in 2x2 (4 panels.) I made a giant spreadsheet of every target I was interested in, listed it's size in arc minutes, and it computed the total panels it would need for each mosiac. It spat out 133~ panels for a full frame sensor @ F3.4, while it spat out 219 panels for an APS-C sensor @ F3.0.

 

I know with the best reducer coma corrector for the APS-C sensor is the Starizona Nexus at 0.75x, making a F4 telescope into a F3. The best 3" corrector for a full frame I've found is possibly a 0.85x reducer, making it F3.4. Going from F3.4 -> F3.0 is 1.2844 faster, with the tradeoff I'd be going from a 1,020~mm focal length down to 900. 

 

So let's say I wanted to image an individual panel for 100 hours on the full frame setup. On the full frame setup that'd be 13,300 hours, and could take 4.5 years (say at 10 hours/night for 290 clear nights a year) to chew through all the targets in a remote observatory. At a $800/peir cost for a heavy pier at Starfront - that'd be a $44k spend. 

 

The APS-C would be 17,049 hours, and 5.87 years, for $56k total spend at $800/mo/pier. I'd estimate the full frame system costs ~3k more when you add the bigger filters/etc. However, it saves $12k on pier fees given it can image larger portions of the sky.

 

The other tough thing is I already have an APS-C color, mono, and nexus coma corrector. So I already have some cost savings going with the APS-C system. I've not yet bought any filters. I also realize that I could shoot all the APS-C friendly targets first then do the full frame ones later. That would be 46 APS-C panels (1.23 years) and 87 full frame panels (3.0 years) for 4.23 total years/$40k total spend at a remote observatory.

 

Anyways, how is the full frame experience on a Newtonian with a 3" focuser?

Edited by Ritaelyn, 24 January 2025 - 08:40 PM.

[Ritaelyn]

I'm also considering the 300/1200 f4 Lacerta Carbon Newtonian - https://teleskop-aus.../FN30012c-new#m

 

Apparently they stopped making them for full frame with 3" focusers - claiming the vigenette is too strong. So with such an expensive purchase and investment - I'd like to check with you guys first.   I've done some ray tracing with various newtonian websites and it seems like the 100mm secondary mirror shouldn't vigenette. The various 3" coma correctors seem to advertise a fully illuminated 44-50mm field.

 

At the end of the day I want the best image quality that a 12" f4 refractor can offer. What are people's thoughts on the Lacerta offering? Thanks! 

[cuzimthedad]

Moving to the DSLR imaging forum...

[kevinkiller]

Ritaelyn,

 

In case you weren't aware the "Heavy" category at Starfront isn't the most economical for that size telescope.

 

You can find remote hosting other places starting around $550/mo

A much more economical setup would be a 10" F4 Newtonian on their "Standard" pier for $299/mo.   Bray Falls shows an example of such a setup in one of his latest videos.

Also, a lot of people regard the Televue Paracorr as the absolute best coma corrector for Newtonian telescopes.   They make a 3" version call the "Big" Paracorr.   It's the only option available from the premium Artesky maker;  https://artesky.it/g...2278161596.html

Edited by kevinkiller, 25 January 2025 - 03:05 PM.

[mayhem13]

Yes….you will need a 3” focuser for use with a FF sensor and a Newtonian. The TV 3” Paracorr has the same 1.15x Barlow effect as the 2” so it will slow down your mirror a bit.

 

The problem becomes diffraction and the large central obstruction and the effects on image resolution…..not to mention the weight and costs of a 3” focuser like a Prima Luce and the big Paracorr. 
 

Now on to the other ‘Newtonian’ problem……collimation within the degree that such long focal lengths and high speeds demand. CDK and RCs are preferred by professionals not just for the shorter length of the instrument but also the stability….once they are collimated, they stay that way….often for months at a time.

 

I’d suggest you look at an imaging array……two smaller scopes. Two 8” mirrors have the same surface area as a single 12. Using an array of say 2 8” RC scopes will in effect give you the same data capture time as a single 12 with more stability and flexibility. And when not reduced, they can cover a FF sensor with just a flattener. 2 8” RCs like the Carbon Star 8 will weigh 33lbs but be much shorted and therefore no sag as the weight is applied along the center of gravity of the mount, not hanging off the back like a newt.

 

Yes….RCs are difficult to collimate…..but as I said earlier….once the primary and focuser are collimated, small tweaks to the secondary are all that is required and that’s extremely easy. Dual 150mm refractors will do just as well…..the reason is regardless of the smaller aperture, the clear aperture is  equivalent to that of an 8” reflector…..and no collimation required…..just a lot more $$$…..two Esprit 150’s are a few sheckles.

[Ritaelyn]

Yes….you will need a 3” focuser for use with a FF sensor and a Newtonian. The TV 3” Paracorr has the same 1.15x Barlow effect as the 2” so it will slow down your mirror a bit.

 

The problem becomes diffraction and the large central obstruction and the effects on image resolution…..not to mention the weight and costs of a 3” focuser like a Prima Luce and the big Paracorr. 
 

Now on to the other ‘Newtonian’ problem……collimation within the degree that such long focal lengths and high speeds demand. CDK and RCs are preferred by professionals not just for the shorter length of the instrument but also the stability….once they are collimated, they stay that way….often for months at a time.

 

I’d suggest you look at an imaging array……two smaller scopes. Two 8” mirrors have the same surface area as a single 12. Using an array of say 2 8” RC scopes will in effect give you the same data capture time as a single 12 with more stability and flexibility. And when not reduced, they can cover a FF sensor with just a flattener. 2 8” RCs like the Carbon Star 8 will weigh 33lbs but be much shorted and therefore no sag as the weight is applied along the center of gravity of the mount, not hanging off the back like a newt.

 

Yes….RCs are difficult to collimate…..but as I said earlier….once the primary and focuser are collimated, small tweaks to the secondary are all that is required and that’s extremely easy. Dual 150mm refractors will do just as well…..the reason is regardless of the smaller aperture, the clear aperture is  equivalent to that of an 8” reflector…..and no collimation required…..just a lot more $$$…..two Esprit 150’s are a few sheckles.

I'm not seeing how two f/8s give the same imaging time as one f/3.4. Isn't pixel entedue purely based on f/ratio? (8/3.4)^2 = 5.5x. For two RC's 5.5x/2 = 2.768, so the newt is still faster. To get the equivalent imaging time I'd need 5.5x RCs. 

Not to mention - you're really limiting FOV at f/8 too! My spreadshet spits out 245.00 full frame panels at a 200m f/8 vs 133.00 panels at 300m f/3.4!  I'd have 1.84x more panels to chew through! 

 

My spreadsheet calculates the pixel etendue of your f/8 RC suggestion to be 7,277. My APS-C sensor 61,352. My Full Frame Sensor to be 47,765. If I 2x2 bin the RC - 29,111.07. So my full frame setup is still 1.64x faster. I still have 245 full frame panels vs 133 panels, 1.84x! So 1.64 * 1.84 = 3.0 RCs needed to one newtonian, so your math was way off. Now I'm 3 standard piers at Starfront vs one heavy. I'm sure if I had 2 RCs on one setup they'd put me in the heavy class, not light. Plus multi setups on one mount is kinda sucky too.

 

My spreadsheet says 1 RC = 35.56 years to image everything I desire, vs 11.74 years on the f/3.4 newtonian. If I put in 3x RCs = 11.85 years. So your 2x RC's was the wrong math.

 

 

I wasn't considering the 3" Paracorr at all because of the 1.15x barlow effect. I was considering the Sharpstar 3" 0.85x MPCC, which speeds it up to f/3.4. 

 

Not to mention but 3x full frame setups on the RCs ignoring the mount is budget busting! $8.3k just per full frame for camera/filters/etc. We're talking just $25k just for the camera gear! LOL. Plus 99 lbs on one mount, that's not even CEM120 territory anymore, we're in a software bisque mount for at least the Paramount MX for $11k. So $25k + $11k + 3x 1.4k carbon stars (4.2k) = 40.2k. Went way over budget buddy, my budget was $20k. At $40k I might as well pop for a nice .5m RC instead. 

 

I'd appreciate it if people read my post here and not suggest inferior setups. There's a reason why I'm drawn to the f/3.4 newtonian. 

 

 

Edit:

 

I saw the above RC only has a 2" focuser, so we can't do full frame on it. That's 456.00 APS-C sized panels at f/8, binned down 2x2 to a 800mm focal length, and I'd need 6 of those to image it in the same time as my full frame f/3.4 setup. 

Edited by Ritaelyn, 27 January 2025 - 02:53 PM.

[Ritaelyn]

Ritaelyn,

 

In case you weren't aware the "Heavy" category at Starfront isn't the most economical for that size telescope.

 

You can find remote hosting other places starting around $550/mo

A much more economical setup would be a 10" F4 Newtonian on their "Standard" pier for $299/mo.   Bray Falls shows an example of such a setup in one of his latest videos.

Also, a lot of people regard the Televue Paracorr as the absolute best coma corrector for Newtonian telescopes.   They make a 3" version call the "Big" Paracorr.   It's the only option available from the premium Artesky maker;  https://artesky.it/g...2278161596.html

Who do you suggest for remote hosting at $550/month?

 

The 10" isn't getting my desired image scale. I want 1,000ml focal length. That's a F/4 system to a 12" F3.4, so the 12" is 38% faster. So I'd have to buy two 10" to one 12". Or get through my desired targets in 16.31 years vs 11.74 of the newtonian (112k pier cost vs 58.7k pier cost). So one 10" does save on pier cost, at the cost of 1.389x longer imaging time.

My spreadsheet computes the total system cost of the following:
 

10" ONTC APS-C - $11,639.83 total system cost including filters, camera, etc. Possibly $9,439.83 if I put it on a CEM40~ but that seems risky vs CEM70. 

12" ONTC APS-C - $12,067.83

12" ONTC Full Frame - $15,092.83

 

So, again, my budget is $20k. Two 10"s come out to $23,279.66, given I don't want to risk CEM40s on a 10". So now at Starfront I'm two standard piers at $600/mo, vs one heavy at $800/mo. I'm saving $200/mo. What's the return on investment on that? $2,400 / 11,639 = 20%, so I don't think it's a bad suggestion. 2x 10"s will image faster.

 

However, that assumes I can sell all the gear for full price when I'm done, which isn't the case, I'd only get 50% value off selling it. So 20% return rate is too opertunistic. I'd be taking an immediate 50% loss if I tried to resell it next day given what I see sells on the used market. So it would take 2.5 years to break even on the $6k lost value in saving $200/mo at Starfront. 

 

I also don't see Bray Falls talking about 10" newts. I do see him having 3x hyperstars on one mount. I've never liked the hyperstar pictures on Astrobin. The weight on the SCT corrector's plate is enormous and makes for some really bad blurry images. I really like the crips images I've seen from the 10" and 12" ONTC newtonians.

 

I'm also considering saving up for my own land vs remote hosting the entire time. So once I have my own land there is no extra ongoing costs with the 12" vs the 10". Plus there might be a chance I can get the 12" under 58" long pier diameter, given its 48" long. I think if I mounted the plate perfectly centered and used some counter weights on it I might be able to get under 58" long diameter. 

 

If I were gonna buy 2x 10s - I think I'd rather buy 2x 12s. Plus the spot diagrams/etc of all the correctors look a lot better on 12" f/4 than they do on 10" f/4.

[Ritaelyn]

I also think people are really under estimating the value of shooting in true Bortle 1-2 class skies in this post too. I have a SQM-L meter. At my home I'm imaging in 17.49 light, no moon out. My best spot that I can get to in one hour, each way, is SQM-L 20.79. At that dark level 20 hours imaging there = 1 hour imaging at home based on this math - 2.5^(20.79-17.49) = 20.56.

 

So let's say I get a setup in SQM-L 21.76 skies, right between bortle 1 and bortle 2.  2.5^(21.76-17.49) = 50x better imaging than at home. 1 hour in those skies = 50 hours imaging at home.

 

2.5^(21.76-20.79) = 2.43x better in a remote setup than what I can get to in an hour. 

 

Given the travel time to get to SQML-L 21.76~ skies takes 2.5 hours - each way - that's 5 hours of travel time that the remote imaging would give me every night. I hate to say it but 2 hour round trip vs 5 hour round trip means I'm actually better off using the imaging time in 20.79 skies than traveling to 21.76 skies, unless I go remote hosted.

 

So remote hosting for my situation provides tremendous value, even at $800/mo pier cost. Let's say at 20 clear nights a month, at 10 hours clear night, at 50x multiplier, it's giving me 10,000 hours equivalent of imaging at home. At the 2.5x multiplier vs traveling - it's giving me 500 more hours, assuming I could travel every night.  Given as I said above - I can only get to my bortle 4~ skies once a month, this is how much remote hosting is giving me:

 

19 nights * 10 hours a night * 50 x multiplier = 9,500 hours

1 night * 10 hours a night * 2.5x multiplier = 25 hours

 

Going remote hosted is giving me 9,525 hours more of integration time a month than what I get at home for what I'm doing, etc. Even with the more expensive $800/mo pier rental, that value is $800 / 9525 hours = $0.08 an hour. So even just making mininum wage means the time savings is worth it to go remote hosted.

[gspinin]

I recently received my teleskop Service ONTC 8” hypergraph Newt. It comes with a 3” focuser and I plan to send it to Starfront with the zwo am5 and asi2600mm duo and set of Antlia 4.5nm LRGBSHO filters. I’ll probably run an ASIAir Pro for simplicity. Cost for the OTA was $3600 + $100 shipping. This was a 4 month wait due to the carbon fiber construction. With the ONtC you’re also able to run two focal lengths by moving the primary mirror position. So for mine, I have a .85x reducer, 680mm at f3.4 and at position 2 (closest position of the primary to the secondary mirror) and a 1.15x coma corrector (920mm at f4.5 and at position 1 — middle slot). See attached images.

 

Best,

Andy (astro_chroma)

Attached Thumbnails

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[mayhem13]

I'm not seeing how two f/8s give the same imaging time as one f/3.4. Isn't pixel entedue purely based on f/ratio? (8/3.4)^2 = 5.5x. For two RC's 5.5x/2 = 2.768, so the newt is still faster. To get the equivalent imaging time I'd need 5.5x RCs. 

Not to mention - you're really limiting FOV at f/8 too! My spreadshet spits out 245.00 full frame panels at a 200m f/8 vs 133.00 panels at 300m f/3.4!  I'd have 1.84x more panels to chew through! 

 

My spreadsheet calculates the pixel etendue of your f/8 RC suggestion to be 7,277. My APS-C sensor 61,352. My Full Frame Sensor to be 47,765. If I 2x2 bin the RC - 29,111.07. So my full frame setup is still 1.64x faster. I still have 245 full frame panels vs 133 panels, 1.84x! So 1.64 * 1.84 = 3.0 RCs needed to one newtonian, so your math was way off. Now I'm 3 standard piers at Starfront vs one heavy. I'm sure if I had 2 RCs on one setup they'd put me in the heavy class, not light. Plus multi setups on one mount is kinda sucky too.

 

My spreadsheet says 1 RC = 35.56 years to image everything I desire, vs 11.74 years on the f/3.4 newtonian. If I put in 3x RCs = 11.85 years. So your 2x RC's was the wrong math.

 

 

I wasn't considering the 3" Paracorr at all because of the 1.15x barlow effect. I was considering the Sharpstar 3" 0.85x MPCC, which speeds it up to f/3.4. 

 

Not to mention but 3x full frame setups on the RCs ignoring the mount is budget busting! $8.3k just per full frame for camera/filters/etc. We're talking just $25k just for the camera gear! LOL. Plus 99 lbs on one mount, that's not even CEM120 territory anymore, we're in a software bisque mount for at least the Paramount MX for $11k. So $25k + $11k + 3x 1.4k carbon stars (4.2k) = 40.2k. Went way over budget buddy, my budget was $20k. At $40k I might as well pop for a nice .5m RC instead. 

 

I'd appreciate it if people read my post here and not suggest inferior setups. There's a reason why I'm drawn to the f/3.4 newtonian. 

 

 

Edit:

 

I saw the above RC only has a 2" focuser, so we can't do full frame on it. That's 456.00 APS-C sized panels at f/8, binned down 2x2 to a 800mm focal length, and I'd need 6 of those to image it in the same time as my full frame f/3.4 setup. 

Ok….so there’s spreadsheet data sets and then there’s reality

 

No 3” CC is going to give you a flat field and full illumination of a FF sensor at that speed…..your best bet is a very high precision primary mirror custom figured….like Lockwood or Ostahowski combined with the Televue….you may get close but expect 10-15% cropping and a serious dent in your bank account. The spot diagrams on the SharpStar 3" are not good.

 

Big secondary equals big obstruction……10% reduction of your 12” primary not to mention the effects of diffraction…..better have plenty of baffling in that tube.

 

I suppose I wasn’t completely clear on the 8” RCs……each with a .67 reducer for an F5.35 at 970FL……each scope weighs under 17lbs……..45 lbs all in with a healthy imaging train. If I’m not mistaken, a 12” native F4 scope will likely weigh in around 50lbs without gear if we assume a premium primary mirror and precision cell.

 

There’s no free lunch here with fast optics……

Edited by mayhem13, 29 January 2025 - 11:38 AM.

[kevinkiller]

Who do you suggest for remote hosting at $550/month?

 

Plus there might be a chance I can get the 12" under 58" long pier diameter, given its 48" long. I think if I mounted the plate perfectly centered and used some counter weights on it I might be able to get under 58" long diameter. 

 

Contact Larry Wilson at astronomyacres.com.  I was once offered a pier for about half the cost of a heavy pier at Starfront with 1-year pre-paid lease.   Ed at DeepSpaceProducts once offered me a pier for around about two-thirds the price of a heavy pier at Starfront.  Both these piers could host at least 65" "swing diameter" scope or even a bigger one.

 

 

The center of RA/DEC to top of saddle on this mount is 3.75".  Compare that to 7" to 8" on other mounts.
https://discord.com/...545768230715503

Maybe that will free up enough "swing" distance.   

 

If you figure out how to  get a 12" newt on a standard pier let me know!!   I'll buy one too.,

Edited by kevinkiller, 29 January 2025 - 03:18 AM.

[Ritaelyn]

Contact Larry Wilson at astronomyacres.com.  I was once offered a pier for about half the cost of a heavy pier at Starfront with 1-year pre-paid lease.   Ed at DeepSpaceProducts once offered me a pier for around about two-thirds the price of a heavy pier at Starfront.  Both these piers could host at least 65" "swing diameter" scope or even a bigger one.

 

 

The center of RA/DEC to top of saddle on this mount is 3.75".  Compare that to 7" to 8" on other mounts.
https://discord.com/...545768230715503

Maybe that will free up enough "swing" distance.   

 

If you figure out how to  get a 12" newt on a standard pier let me know!!   I'll buy one too.,

Thank you for mentioning a few competitors! I really appreciate it!

Then the discord link isn't working for me. What mount did you link?

[Ritaelyn]

Contact Larry Wilson at astronomyacres.com.  I was once offered a pier for about half the cost of a heavy pier at Starfront with 1-year pre-paid lease.   Ed at DeepSpaceProducts once offered me a pier for around about two-thirds the price of a heavy pier at Starfront.  Both these piers could host at least 65" "swing diameter" scope or even a bigger one.

 

 

The center of RA/DEC to top of saddle on this mount is 3.75".  Compare that to 7" to 8" on other mounts.
https://discord.com/...545768230715503

Maybe that will free up enough "swing" distance.   

 

If you figure out how to  get a 12" newt on a standard pier let me know!!   I'll buy one too.,

 

I've decided the following:

 

1. I've decided to get a full frame sensor.

2. I decided to get the 12" ONTC from TS - they have a conical mirror version I missed that is even lighter weight, they're making these mirrors in house vs the GSO/synta mirrors they're making the other ONTC mirrors from.

 

 

I searched on the Starfront discord link - I saw someone mention they thought the CEM70 was 3.75" saddle length. Sadly I emailed iOptron - its 203mm (8") for CEM70, 235mm for CEM120 (9.25mm). 

 

I've not found any mounts yet that could handle a Newt with less than 4" saddle length yet. These are the lengths of other vendors I've contacted:

10 micron mounts:

GM1000 HPS: 148 mm (5.8 inches, 55 lbs payload)
GM2000 HPS II: 178 mm (7 inches, 110lb payloads, 10micron recommends I put my newt in ths.)
GM3000 HPS: 231 mm (9 inches, 220lb payload)
GM4000 HPS II: 299 mm (11.77 inches, 330 lbs payload.)

 

EQ-6R: 

260mm, 10.2 inches

 

JTW mounts:

Someone at Starfront measured a Trident GTS and took a picture. It was 9 inches including the OTA's dovetail.

The OTA's dovetail is 1.5 inches, so it's 7.5 inches to make it compariable to the above measurements.

 

The 12" ONTC has a 14" diameter tube, its 48" long, the dovetail and rings add 1.5 inches radius.

 

A reasonable upper bound estimate is taking the pythagorean theorem to solve for radius, then multiply by 2 for diameter, given how Starfront measures radius vs the radius from the RA axis along the DEC axis.

 

So far for the 12" newtonian mounted perfectly centered on a 7.5" saddle length mount, with 1.5 inch dovetail

 

sqrt( (7.5+1.5+14)^2 + 24^2)  * 2 = 66 inch swing diameter

 

However, we know a EQ6-R and a 10" seems to be within 58" swing diameter

 

sqrt( (10.2+1.5+(14/12) * 10 )^2 + 20^2) * 2 = 61.51

 

Unfortunately only a 3.5" radius mount or less will be under the 10's upper bound on swing radius sadly.

 

Given math says a 10" should be a heavy pier it makes me wonder if there is some leeway at Starfront or if they're measuring it impreciesly. It should be the diagonal of the rectangle going straight up the dec axis from the RA axis to the longest point of the OTA, assuming no dangling cables/etc. 

 

I'd probably order something within the 7-7.5 swing radius. I'm leaning towards either the $6k JTW Trident GTS or the $16k GM2000 HPS II.

[Ritaelyn]

Contact Larry Wilson at astronomyacres.com.  I was once offered a pier for about half the cost of a heavy pier at Starfront with 1-year pre-paid lease.   Ed at DeepSpaceProducts once offered me a pier for around about two-thirds the price of a heavy pier at Starfront.  Both these piers could host at least 65" "swing diameter" scope or even a bigger one.

 

 

The center of RA/DEC to top of saddle on this mount is 3.75".  Compare that to 7" to 8" on other mounts.
https://discord.com/...545768230715503

Maybe that will free up enough "swing" distance.   

 

If you figure out how to  get a 12" newt on a standard pier let me know!!   I'll buy one too.,

 

I realized for the 10" if it's 7.5 inches or less saddle distance the 10" likely is under 58 swing diameter:

sqrt( (7.5+1.5+(14/12) * 10 )^2 + 20^2) * 2 = 57.51"

 

sqrt( (7.5+1.5+(14))^2 + 24^2) * 2 = 66.48"

 

Only way for a 12" to be have a good chance at a less than 58" swing diameter is if it were on a strainwave mount and you directly screwed in the dovetail into the tube, no rings.

 

sqrt( (3+(14))^2 + 24^2) * 2 = 58.82

 

So, I decided to research the strainwave mounts and sadly they have too much periodic error for 1,200mm focal length. Their periodic error is +-15 arc seconds, which is .64 arc second pixels, and +- 23 pixels (so up to 48 pixel movement.) 

 

You'd have to do short exposures given that, which sucks stacking wise and on a SNR basis.

 

Most recommended mounts are +-0.7 arc seconds. 

 

I think I value imaging with a 12" more than I do with a 10". The aperture alone isn't too much a difference, but the light loss starts to get significant for full frame given I'd have to use the same 100mm secondary and it's 40% on the 10" vs 33% on the 12 inch. It's a 228mm vs 282mm effective diameter when you account for the differences in surface area. Roughly the 12" has 52% more pixel etendue.

 

I think I'm going to roll the dice with ordering a JTW Trident GTS for the OTA and see how it goes. Thank you!  

[lambermo]

Any update ?

[calypsob]

I fell in love with doing astrophotography by doing short exposure imaging on my 12" newtonian dobsonian mounted telescope. I've been doing this since November. I'm considering buying a 12" F4 ONTC Newtonian reflector + an equitorial mount for it. How well does the ONTC Newtonians work with a full frame (IMX455) setup such as with the ASI6200MM or Player One Zeus 455M Pro, assuming it has the proper 100mm secondary mirror? 

 

I'm also on the fence of sending it to a remote observatory like Starfront, vs keeping it here with me. I live in bortle 8 skies, but I have access to bortle 4.5 - 5 within 60 minutes, and bortle 1 within 2.5 hours. I'm only able to visit bortle 1 areas I'd say once every 2 months - possibly once every month. I know 1 hour in bortle 1 = 45 hours in my bortle 8 skies.

 

My desires are doing medium-field mosiacs astrophotography of deep space objects - nebulas like m42, m45, galaxies such as m31, leo triplet (m65, m66), other nearer galaxies, etc. I want to shoot in LRGB + SHO. I'm willing to budget up to $20k for the entire system - OTA, mount, and filters. The ONTC weighs 17kg (37lbs) and my imaging equipment weighs 7 lbs, for 44 lbs total mount weight. I'd likely throw it on a CEM70 if I travel with it. If I go remote I might try the CEM70, but I'd be prepared to buy a CEM120 for it given it might act like a wind sail. Given my experiences with short exposure photography on the dob - I don't mind seeing if I can write code or a plugin to switch to short exposures if wind > X mph in NINA.   

 

I made a spreadsheet of a list of all the targets I could think of so far and an APS-C camera spat out a 2x3 panel (6 panels) for andromeda, while a full frame sensor could do it in 2x2 (4 panels.) I made a giant spreadsheet of every target I was interested in, listed it's size in arc minutes, and it computed the total panels it would need for each mosiac. It spat out 133~ panels for a full frame sensor @ F3.4, while it spat out 219 panels for an APS-C sensor @ F3.0.

 

I know with the best reducer coma corrector for the APS-C sensor is the Starizona Nexus at 0.75x, making a F4 telescope into a F3. The best 3" corrector for a full frame I've found is possibly a 0.85x reducer, making it F3.4. Going from F3.4 -> F3.0 is 1.2844 faster, with the tradeoff I'd be going from a 1,020~mm focal length down to 900. 

 

So let's say I wanted to image an individual panel for 100 hours on the full frame setup. On the full frame setup that'd be 13,300 hours, and could take 4.5 years (say at 10 hours/night for 290 clear nights a year) to chew through all the targets in a remote observatory. At a $800/peir cost for a heavy pier at Starfront - that'd be a $44k spend. 

 

The APS-C would be 17,049 hours, and 5.87 years, for $56k total spend at $800/mo/pier. I'd estimate the full frame system costs ~3k more when you add the bigger filters/etc. However, it saves $12k on pier fees given it can image larger portions of the sky.

 

The other tough thing is I already have an APS-C color, mono, and nexus coma corrector. So I already have some cost savings going with the APS-C system. I've not yet bought any filters. I also realize that I could shoot all the APS-C friendly targets first then do the full frame ones later. That would be 46 APS-C panels (1.23 years) and 87 full frame panels (3.0 years) for 4.23 total years/$40k total spend at a remote observatory.

 

Anyways, how is the full frame experience on a Newtonian with a 3" focuser?

Star front is not a good deal for big equipment. Many other places offer much more for less on big stuff. The standard and smaller packages are where star front shines. I imagine that if starfront slows growth or looses momentum, large pier pricing will drop dramatically. 
 

a 12” newt running remote will be burdensome of dust and cannot be easily cleaned. Mine is a truss so I have additional concern about light leaks from neighboring leds on equipment. This can be an issue on closed tubes too.

 

If you end up going fullframe, paracorr imo is the best of all correctors. 
The nexus with color will be fine, you may want filters though so you can image during moonlit cycles.