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SCT autoguiding that can be transferred for future upgrade


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Hi guys! I'm currently the owner of a Celestron Nexstar 6SE and have been infected with the¬† Astrophotography bug. It has taken a hold of me and is forcing¬†me to go out and purchase an HEQ5 mount¬†ūü•Ķ. I have come on here to seek the opinion of more experienced Astronomers regarding my set up.¬†

I'm in a somewhat unique position re: upgrading my kit for AP. The reason I originally purchased the 6SE was to use it for visual use for an 8 week road trip through the Australian outback coming up in a few months. The OTA is a fairly compact unit to pack for a trip and it provides a fantastic visual view. Since making this purchase the AP bug has bitten and I have spent a bit of time playing around with short exposure AP using a DSLR on prime focus with the stock mount. Loving it. I'm about to drop the hammer on an HEQ5 to enable longer exposures. The next step from here will naturally be an Autoguiding setup. 
From what I understand the SCT OTA's are better paired with an OAG for guiding. Is it possible to get a guidescope and camera working well enough for 5 minute exposures on an SCT? I would like to still use this compact OTA with the HEQ5 for my trip but I think I will eventually sell the 6se package to fund a different OTA, thus why I am enquiring about using a guidescope for this set up. I would like to take the guidescope with me to use with my next OTA to save money.
Does anybody have any recommendations of another OTA that would be suitable for visual and AP on my trip that is also compact? 

Thanks for your time


Stefan
 

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Do you have a budget in mind? It'll probably help with recommendations ūüĎć

For the additional OTA I'd suggest a "fast" refractor so you have something for wider field, may as well make the most of the dark skies there. For example on a budget https://www.firstlightoptics.com/startravel/skywatcher-startravel-80-ota.html or https://www.firstlightoptics.com/startravel/skywatcher-startravel-102t-ota.html

Or with a bit more cash - https://www.firstlightoptics.com/pro-series/skywatcher-evostar-80ed-ds-pro-ota.html although the skies the limit once you star on ED glass, triplets, quads etc

It sounds like a small guidescope combo would be more suitable, but someone with more experience will be along soon I suspect

 

 

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I'm guiding my Celestron C8 with an SVBONY 60mm guidescope and ZWO ASI290mm mini on a Celestron Advance GT mount. Haven't gone above 3 minutes yet as I only started late spring and it's not dark enough for long exposures right now but I can't see any reason why longer exposures shouldn't be possible. Guiding with PHD2 and I rarely see a flicker off target.  At 3 minutes, my stars are nice and round :)

Graeme

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12 hours ago, doublevodka said:

Do you have a budget in mind? It'll probably help with recommendations ūüĎć

For the additional OTA I'd suggest a "fast" refractor so you have something for wider field, may as well make the most of the dark skies there. For example on a budget https://www.firstlightoptics.com/startravel/skywatcher-startravel-80-ota.html or https://www.firstlightoptics.com/startravel/skywatcher-startravel-102t-ota.html

Or with a bit more cash - https://www.firstlightoptics.com/pro-series/skywatcher-evostar-80ed-ds-pro-ota.html although the skies the limit once you star on ED glass, triplets, quads etc

It sounds like a small guidescope combo would be more suitable, but someone with more experience will be along soon

 

Hey I appreciate your response. Both those scopes are within my budget. I would say 500 pounds would be my upper limit, but I see this as a long term investment so I'm open to stretching the budget. 
Do you think there is a major diference between the 6SE OTA and the 80ED for AP? I haven't had any problems using the SCT thus far and have been considering selling the Mount and PowerTank to fund an OAG and guide cam. 

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12 hours ago, jacko61 said:

I'm guiding my Celestron C8 with an SVBONY 60mm guidescope and ZWO ASI290mm mini on a Celestron Advance GT mount. Haven't gone above 3 minutes yet as I only started late spring and it's not dark enough for long exposures right now but I can't see any reason why longer exposures shouldn't be possible. Guiding with PHD2 and I rarely see a flicker off target.  At 3 minutes, my stars are nice and round :)

Graeme

Interesting! I was told that due to mirror shift the Guide scope solution is not entirely practical for the SCT. I'm surprised to here you are getting decent subs out of that arrangement. Are you retaining most of the frames at 180 seconds?

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Yes,  this M51 is one of my first attempts at AP - 180 seconds at ISO 800.  Only 20 subs but I think I only rejected 2 of them - there does seem to be a fraction of ovalling but it was my first imaging session.  I find now that my guiding with PHD2 is very stable once it gets going although I'm still using the ST4 interface rather than ascom.

 

m51.jpg

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8 hours ago, Stefan87 said:

Hey I appreciate your response. Both those scopes are within my budget. I would say 500 pounds would be my upper limit, but I see this as a long term investment so I'm open to stretching the budget. 
Do you think there is a major diference between the 6SE OTA and the 80ED for AP? I haven't had any problems using the SCT thus far and have been considering selling the Mount and PowerTank to fund an OAG and guide cam. 

Yes there will be a difference certainly, SCT's have a very long focal length so are more "zoomed in", fast refractors have a short focal length for a wider field.

 

I've done a quick comparison below, didn't know the DSLR you were using so picked one at random

 

6SE - http://astronomy.tools/calculators/field_of_view/?fov[]=109||83||1|1|0&messier=31 (crop sensor DSLR)

         http://astronomy.tools/calculators/field_of_view/?fov[]=109||142||0.85|1|0&messier=31 (full frame DSLR)

SW 80 DS Pro - http://astronomy.tools/calculators/field_of_view/?fov[]=3||83||1|1|0&messier=31 (crop sensor DSLR)

                          http://astronomy.tools/calculators/field_of_view/?fov[]=3||142||0.85|1|0&messier=31 (full frame DSLR)

 

As you can see the difference is quite large!

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Taking the long view, an OAG is best for your 6SE + HEQ5, and won't make guiding any worse on a shorter FL OTAs.

An OAG is comparable in price with a decent guidescope with suitably rigid rings, the guidecam will be more expensive, as it's best to go with a sensitive mono camera.

I use A LodeStar 2, I'm not up to speed with suitable newer cameras.

Michael

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On 23/07/2021 at 17:16, doublevodka said:

Yes there will be a difference certainly, SCT's have a very long focal length so are more "zoomed in", fast refractors have a short focal length for a wider field.

 

I've done a quick comparison below, didn't know the DSLR you were using so picked one at random

 

6SE - http://astronomy.tools/calculators/field_of_view/?fov[]=109||83||1|1|0&messier=31 (crop sensor DSLR)

         http://astronomy.tools/calculators/field_of_view/?fov[]=109||142||0.85|1|0&messier=31 (full frame DSLR)

SW 80 DS Pro - http://astronomy.tools/calculators/field_of_view/?fov[]=3||83||1|1|0&messier=31 (crop sensor DSLR)

                          http://astronomy.tools/calculators/field_of_view/?fov[]=3||142||0.85|1|0&messier=31 (full frame DSLR)

 

As you can see the difference is quite large!

Ok that makes alot of sense. But FOV aside, is there a remarkable difference in image quality? Also, does an OAG work well with a refractor? I'm thinking if I purchase an OAG guide setup now and sell my 6se in the future for a refractor I would able to take it with me to use on the refractor.

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On 22/07/2021 at 12:02, doublevodka said:

Do you have a budget in mind? It'll probably help with recommendations ūüĎć

For the additional OTA I'd suggest a "fast" refractor so you have something for wider field, may as well make the most of the dark skies there. For example on a budget https://www.firstlightoptics.com/startravel/skywatcher-startravel-80-ota.html or https://www.firstlightoptics.com/startravel/skywatcher-startravel-102t-ota.html

Or with a bit more cash - https://www.firstlightoptics.com/pro-series/skywatcher-evostar-80ed-ds-pro-ota.html although the skies the limit once you star on ED glass, triplets, quads etc

It sounds like a small guidescope combo would be more suitable, but someone with more experience will be along soon I suspect

 

 

The Startravel fast refractors are entirely unsuitable for astrophotography. The numbers look good but they have massive chromatic and spherical aberration and their focusers are primitive and induce tilt. These issues are not so critical for visual use but the camera makes the most of each defect!  Do not buy these for imaging.

Olly

 

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I started my astrophotography journey with upgrading from a Celestron 127 SLT which is a slightly cheaper and smaller scope than the Nexstar 6SE.

I paired with a Skywatcher EvoStar 50mm guidescope onto the HEQ5 and took pictures with my DSLR. It worked great! Just worth noting the extremely 'zoom' of the picture can make finding targets difficult, and the slow focal ratio means you need to spend a long time on your targets. For reference, I was doing 3 minute subs on that setup to get M101 to resolve clearly.

I moved up to a William Optics refractor which is so much easier to work with and much 'faster' on the focal ratio, but more cash of course. You may find you start tinkering with the Nexstar's OTA and then when you settle in to the hobby and find what you like, then move up to a new scope.

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12 hours ago, Stefan87 said:

Ok that makes alot of sense. But FOV aside, is there a remarkable difference in image quality? Also, does an OAG work well with a refractor? I'm thinking if I purchase an OAG guide setup now and sell my 6se in the future for a refractor I would able to take it with me to use on the refractor.

It's very hard to comment on image quality as there are so many factors such as seeing, mount accuracy, camera suitability for the scope etc - there are many threads if you go digging which will explain far better than I can.

It's really a horses for courses thing, no scope does everything well is the short answer, most experienced astronomers seem to have at least a couple of scopes for different scenarios (or specialise in something specific), long focal length for small targets such as planets, double stars etc, then short focal length for nebulas, galaxies, clusters etc

This hobby can really be a bit of a rabbit hole, for example as a curveball you could go down the hyperstar route with the 6SE which would give you the wider field and better light gathering capability see below for an example

As Olly pointed out I would avoid the ST80 budget option, whilst many love it, it's not ideal for photography and it seems you want to get the best out of your kit while you are there so a short, well corrected ed glass refractor would be a better travel companion, but again there are many options, not just the one I mentioned

 

 

Edited by doublevodka
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In your position I'd be more inclined to travel with a smallish refractor than an SCT, especially if bouncing along in the outback! There are lots on the market, from Takahashi downwards. They take more rattling and shaking without going out of collimation and they reach ambient temperature more quickly, which might also be a big deal.  Vast, wide open dark skies are also perfect for wide fields of view and these are less demanding on guiding, which might mean more time collecting light and less time tuning the kit each night.

Olly

 

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Thanks for the responses. You make a very good point regarding the SCT not being the most suitable for travelling. I'm very close to deciding to sell my 6se and just take the HEQ5 and a new refractor. The trip has been delayed somewhat with the current Covid situation in Australia so I have some time to breathe and get it right. Thanks for the help and thoughts!

 What do you guys think of this Scope for imaging Nebula/Galaxies? If I purchase a ZWO OAG and an ASI120mm mini, will this be a guiding setup I can use with any configuration? Including the 6se? https://skywatcheraustralia.com.au/product/120-az3-refractor/

Thanks again
 

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1 hour ago, Stefan87 said:

Thanks for the responses. You make a very good point regarding the SCT not being the most suitable for travelling. I'm very close to deciding to sell my 6se and just take the HEQ5 and a new refractor. The trip has been delayed somewhat with the current Covid situation in Australia so I have some time to breathe and get it right. Thanks for the help and thoughts!

 What do you guys think of this Scope for imaging Nebula/Galaxies? If I purchase a ZWO OAG and an ASI120mm mini, will this be a guiding setup I can use with any configuration? Including the 6se? https://skywatcheraustralia.com.au/product/120-az3-refractor/

Thanks again
 

Again, that's an F5 refractor, meaning it has a very fast F ratio. The faster the F ratio, the harder it is for the lens to bring all the colours to the same focal plane. The larger the objective, the more this becomes difficult. This is quite a large refractor for F5 so it will never have the kind of colour correction needed for imaging. It describes itself as an achromat, not an apochromat, meaning it has limited colour correction. Even the best apochromats are not perfect so I wouldn't consider an achromat for imaging. The camera is more demanding on colour correction than the eye.

Although it's an old design, this one https://www.firstlightoptics.com/pro-series/skywatcher-evostar-80ed-ds-pro-ota.html  is widely regarded as hitting the sweet spot between price and performance, visually and with a camera. For imaging you'd need the dedicated field flattener. It does not try to reach an unrealistic F ratio. (I have an F5 refractor but the price new would be about 12x this. Fast photographic optics are extremely expensive.)

You do not have much aperture with 80mm for visual observing but, under clear Oz skies, you would get stunning wider views. In a nutshell the visual and photographic requisites are fundamentally contradictory, especially without a big budget.

Olly

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2 hours ago, Stefan87 said:

Thanks for the responses. You make a very good point regarding the SCT not being the most suitable for travelling. I'm very close to deciding to sell my 6se and just take the HEQ5 and a new refractor. The trip has been delayed somewhat with the current Covid situation in Australia so I have some time to breathe and get it right. Thanks for the help and thoughts!

 What do you guys think of this Scope for imaging Nebula/Galaxies? If I purchase a ZWO OAG and an ASI120mm mini, will this be a guiding setup I can use with any configuration? Including the 6se? https://skywatcheraustralia.com.au/product/120-az3-refractor/

Thanks again
 

If I‚Äôm understanding you correctly¬†you‚Äôre¬†planning on taking the HEQ5 on the trip? I‚Äôm not sure how you are planning to travel but that that would be a bigger hassle than even the SCT in my mind. That‚Äôs going to be ~20kg of weight when you factor in counter weights and tripod. I even gave up carrying that in and out my house ūüėÜ

I agree with the others regarding a portable refractor but if you are planning to do astrophotography as you travel I would seriously consider one of the portable star trackers on the market paired with a short focal length refractor. 

Edited by Icesheet
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2 hours ago, Stefan87 said:

Thanks for the responses. You make a very good point regarding the SCT not being the most suitable for travelling. I'm very close to deciding to sell my 6se and just take the HEQ5 and a new refractor. The trip has been delayed somewhat with the current Covid situation in Australia so I have some time to breathe and get it right. Thanks for the help and thoughts!

 What do you guys think of this Scope for imaging Nebula/Galaxies? If I purchase a ZWO OAG and an ASI120mm mini, will this be a guiding setup I can use with any configuration? Including the 6se? https://skywatcheraustralia.com.au/product/120-az3-refractor/

Thanks again
 

If you're going to sell the 6se then now is as good a time as any, the used market it certainly pretty buoyant!

I'd also look at the used market for the refractor as there are many people selling kit currently, keep an eye on the forum too but for example a quick search externally brought up this which has the field flattener, case and a bahtinov mask to give you a quick example https://www.astrobuysell.com/uk/propview.php?view=175963 

If you really, really must have something with a long focal length and compact size, maybe take a look at the 127 mak? They are generally a bit more robust than the average sct and from what I've seen can produce some good results, for example again a quick search turned this up 

Putting all that aside though, personally if I was travelling through Australia and planning on imaging I'd be going widefield and squeezing out the best refractor and camera combo from my budget to make the most of the dark and wide open skies 

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On 22/07/2021 at 08:34, Stefan87 said:

Hi guys! I'm currently the owner of a Celestron Nexstar 6SE and have been infected with the¬† Astrophotography bug. It has taken a hold of me and is forcing¬†me to go out and purchase an HEQ5 mount¬†ūü•Ķ. I have come on here to seek the opinion of more experienced Astronomers regarding my set up.¬†

I'm in a somewhat unique position re: upgrading my kit for AP. The reason I originally purchased the 6SE was to use it for visual use for an 8 week road trip through the Australian outback coming up in a few months. The OTA is a fairly compact unit to pack for a trip and it provides a fantastic visual view. Since making this purchase the AP bug has bitten and I have spent a bit of time playing around with short exposure AP using a DSLR on prime focus with the stock mount. Loving it. I'm about to drop the hammer on an HEQ5 to enable longer exposures. The next step from here will naturally be an Autoguiding setup. 
From what I understand the SCT OTA's are better paired with an OAG for guiding. Is it possible to get a guidescope and camera working well enough for 5 minute exposures on an SCT? I would like to still use this compact OTA with the HEQ5 for my trip but I think I will eventually sell the 6se package to fund a different OTA, thus why I am enquiring about using a guidescope for this set up. I would like to take the guidescope with me to use with my next OTA to save money.
Does anybody have any recommendations of another OTA that would be suitable for visual and AP on my trip that is also compact? 

Thanks for your time


Stefan
 

I‚Äôve¬†used an 8‚ÄĚ Celestron SCT on an AVX mount.

I use a Skywatcher StarTravel 80 as the guide scope with ASI ZWO 120 mini as guide camera.

5 minutes guiding is the best I’ve managed, it did need very good polar alignment tho.

You¬†should manage that more easily with your 6‚ÄĚ

 

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Thanks so much for the in depth and comprehensive replies! Definitely has given me a lot to consider. That's a shame about that scope Olly! In their description they say it is perfect for Astrophotography but I guess this is another "too good to be true moment". 

I'm gonna stew on this for a bit and not act too hastily. There have been solid points made about the weight of the HEQ5 and travelling. I'm travelling in a Campervan and have freed up/created more space since my last trip for this specifically. Well, for photography in general. I will prematurely work out some rough weights and make sure I'll still be under before getting too excited.

If I may ask another question regarding OAG's? From what I've read, "once you go OAG you never go back" is my take on the opinion of people who have tried both Guide¬†Scopes and OAG. For this reason, and for the sake of getting some decent guiding going right away, would an OAG be the smartest investment into guiding in order to "futureproof" myself in this hobby?¬†Also, Would the ZWO OAG and the ASI120MM Mini be fine to get started with my DSLR as part of the image train on my 6SE? I need 105 mm spacing from my focal reducer, and I feel this should be easily achievable if I place the OAG directly in front of the DSLR. I'm just concerned ZWO have designed their OAG to be used in conjunction with their Imaging camera. This is the cheapest arrangement I can find, and I'm hoping that Mono camera will be perfect but I'm once more concerned this will be another "too good to be true" moment¬†ūüėÖ

Thanks very much for your help! 

Stefan

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50 minutes ago, Stefan87 said:

There have been solid points made about the weight of the HEQ5 and travelling. I'm travelling in a Campervan and have freed up/created more space since my last trip for this specifically. Well, for photography in general. I will prematurely work out some rough weights and make sure I'll still be under before getting too excited.

If you‚Äôre travelling in a camper van and will be setting up close to it then it‚Äôs maybe not as much of an issue as I thought. However, still a good idea to check it all out as you say ūüĎćūüŹĽ

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1 hour ago, Stefan87 said:



If I may ask another question regarding OAG's? From what I've read, "once you go OAG you never go back" is my take on the opinion of people who have tried both

I use both and wouldn't bother with an OAG on an instrument that didn't need it.

Olly

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