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First night out with EQ6-R Pro

Astrophotography DSO Imaging Polar Alignment
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#1 rrbailey89

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Posted 17 August 2022 - 07:34 AM

Hello everyone,

Seeking advice.

Tonight was my first night out with the EQ6-R Pro. It is an upgrade for my from the fork arm that came with my Celestron 8SE.

I watched lots of videos on YouTube about how to get the mount to communicate with N.I.N.A and boy did I still struggle tonight. EQMOD does not like getting close to that meridian until you get that set up, which was an item I had not even considered on my first night out checklist, nonetheless I believe that I got that set up.

I went into the night knowing that I was going to use the plugin in N.I.N.A called Three Point Polar Alignment (TPPA) to polar align due to structures blocking my view of Polaris. I am at a lower latitude so Polaris is about house height.

That in itself was an effort because it seems that N.I.N.A is able to plate solve about 95% of the time using ASTAP when I use the framing wizard, but TPPA is more finicky. However it eventually got its 3 plates and I adjusted the mount. I then ran it again because it warned me that the first time I was quite off and it was unreliable. This second time I did not get that warning and I got the margin of error to less than 00,00',45" for both AZ and ALT.

After this was accomplished I was blown away by the tracking ability of this mount compared to my fork arm even when I was using a wedge. I was able to take up to a 5 minute exposure and although it doubled all the stars it still looked great.

I paint this picture because now I would like to find out from this community any advice to help me get the longest exposures possible without a guide camera. I have attached this image of Andromeda I took tonight so you can see my starting point so to say. This image was put together from 25 90sec exposures at 640ISO with a Sony A7III and a Celstron 8SE using the EQ6-R Pro mount and I edited it in photoshop for about 5 minutes.

Like I said I already love this mount, I just want to get better with it.

Now I thought that the stars were properly focused but now im not so sure, I am not sure if whats going on in this image is a focus issue, a star trailing issue, or both. Any help would be appreciated.

dssjjkv.png

Edit: I forgot to add that I have an ASI178MC in the mail hopefully arriving soon.

Edited by rrbailey89, 17 August 2022 - 06:16 PM.

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#2 Tapio

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Posted 17 August 2022 - 08:09 AM

You have little trailing but no wonder at that focal length and 90 sec exposure.

I think you could try maybe 60 sec exposures to get better stars (at least most of the exposures).

 

To make it easier and better get a focal reducer - and don't be afraid of autoguiding.


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#3 revans

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Posted 17 August 2022 - 08:22 AM

I often use an EQ6-R Pro mount.  How long you can get away using tracking without guiding depends on your focal length and on your sub exposure time.  For example, I don't absolutely need to guide at 530mm focal length as long as I keep my sub exposures between 30 sec and 1 minute depending on how good my polar alignment is.  At a focal length of 2000mm focal length I can get away with 15 sec unguided sub exposures but not longer.  My sky is about Bortle 5-6 so the longest sub exposure I can take even with guiding is about 3 minutes, otherwise the sky washes out at about 5 minute sub exposure time.  Of course if I use narrow band filters then I can use longer sub exposure times with guiding. 

 

Some people think that shorter sub exposures (30 sec or 1 minute sub exposures) are actually a good thing as maybe you are more likely to take advantage of short intervals of better atmospheric seeing, and a satellite only ruins one exposure.  But most people like to do 3 to 5 minute sub exposures which requires guiding, and there are those that like 10 to 15 minute sub exposures.  I assume these guys use filters or have dark skies.  

 

Rick


Edited by revans, 17 August 2022 - 08:24 AM.


#4 idclimber

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Posted 17 August 2022 - 08:28 AM

I suspect you have many issues affecting this image. The first is your choice of M31. This is a huge target and needs a much shorter focal length to capture it. You are only seeing the core of this target with that scope even with the full frame Sony. 

 

The stars look wonky because of tracking, focus and probably because you are also not using a reducer to correct the field of the SCT. You also probably have not figured out collimation. 

 

To get good stars with an SCT without guiding will require a difference mount. Probably one with absolute encoders (about 20 grand), otherwise you will have to use a OAG. This is after you add a reducer and change cameras; because the full frame is not ideal either unless you move to an Edge or one of the SCTs with he 3.25" threads that can accept a reducer that supports full frame. 

 

Imaging with an SCT is a money pit. Either you suffer with relatively poor images or you spend. It is also a lot more difficult. Not a little bit harder, but a LOT. Like climbing Everest on your first climbing trip. You will get a lot farther and faster on this path to Astrophotography if your next purchase is a 80mm refractor. 



#5 bobzeq25

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Posted 17 August 2022 - 08:50 AM

Help.

 

Autoguide.  This is not a close call.  You can easily reduce tracking error by a factor of 10, and then can choose the proper subexposure.  Autoguiding is not some esoteric technique, it's fundamental to using the inexpensive mounts most of us use.

 

This is tougher, but it's still my (strong) recommendation.  Learning imaging (which is a different task than imaging) with the 8 inch scope; long focal length, heavy, slow, is hard, regardless of mount.  It's an expert's scope.  The fastest/cheapest/best way to become more expert would be to get a smaller scope, something like this.  Short, light, fast, is the way to go when learning imaging.

 

https://www.astronom...fpl-53-f-6.html


Edited by bobzeq25, 17 August 2022 - 09:01 AM.

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#6 oldstargazer

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Posted 17 August 2022 - 08:54 AM

Also don't be afraid to double the iso and cut the exposure time in half. I was a film user way back in the day and the iso in film made a hughe difference in the grain size but with digital no so much. I use a T3i these days and have experimented with various iso and changing the exposure times to match the changes and found there was so little change in what was captured I am no longer avoiding 1600 iso. If I am fighting some high winds causing a little mount shake I will up the iso and cut the times and that usually gets rid of that artifact. So anyway the good thing about digital is you can take some shots and take a look, if you don't like what you see then reshoot with different settings and carry on. It was a lot harder to try stuff back in the film days.

 

Have fun and don't be afraid of experimenting, you don't know what you can do until you try it....



#7 revans

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Posted 17 August 2022 - 09:25 AM

I suspect you have many issues affecting this image. The first is your choice of M31. This is a huge target and needs a much shorter focal length to capture it. You are only seeing the core of this target with that scope even with the full frame Sony. 

 

The stars look wonky because of tracking, focus and probably because you are also not using a reducer to correct the field of the SCT. You also probably have not figured out collimation. 

 

To get good stars with an SCT without guiding will require a difference mount. Probably one with absolute encoders (about 20 grand), otherwise you will have to use a OAG. This is after you add a reducer and change cameras; because the full frame is not ideal either unless you move to an Edge or one of the SCTs with he 3.25" threads that can accept a reducer that supports full frame. 

 

Imaging with an SCT is a money pit. Either you suffer with relatively poor images or you spend. It is also a lot more difficult. Not a little bit harder, but a LOT. Like climbing Everest on your first climbing trip. You will get a lot farther and faster on this path to Astrophotography if your next purchase is a 80mm refractor. 

But is it an SCT issue or just a focal length issue.  With a focal reducer, the main problem with an SCT is the absolute requirement to use good flats.  Still, it is true that you have to crop out a bit of peripheral coma most of the time.  Apart from those two issues, I don't have much of a preference between an SCT and a refractor as long as the imaging focal length is the same.  The higher the focal length then the more grief you experience. 

 

Rick



#8 rrbailey89

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Posted 17 August 2022 - 02:11 PM

You have little trailing but no wonder at that focal length and 90 sec exposure.
I think you could try maybe 60 sec exposures to get better stars (at least most of the exposures).

To make it easier and better get a focal reducer - and don't be afraid of autoguiding.


Thanks! I had no idea that focal length would affect trailing.

#9 rrbailey89

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Posted 17 August 2022 - 02:31 PM

I suspect you have many issues affecting this image. The first is your choice of M31. This is a huge target and needs a much shorter focal length to capture it. You are only seeing the core of this target with that scope even with the full frame Sony.

The stars look wonky because of tracking, focus and probably because you are also not using a reducer to correct the field of the SCT. You also probably have not figured out collimation.

To get good stars with an SCT without guiding will require a difference mount. Probably one with absolute encoders (about 20 grand), otherwise you will have to use a OAG. This is after you add a reducer and change cameras; because the full frame is not ideal either unless you move to an Edge or one of the SCTs with he 3.25" threads that can accept a reducer that supports full frame.

Imaging with an SCT is a money pit. Either you suffer with relatively poor images or you spend. It is also a lot more difficult. Not a little bit harder, but a LOT. Like climbing Everest on your first climbing trip. You will get a lot farther and faster on this path to Astrophotography if your next purchase is a 80mm refractor.


I choose M31 simply because I needed to point it at something to get some practice. Is there something else in the same region of sky I could have used to get her potentially better results?

I am not using a reducer. Nor have I considered looking at collimation. The OTA is only a few months old and I think it's collimation is probably still good from the factory.

It sounds like I should look into guiding. Why is imaging with a refractor so much easier than with an SCT?

#10 gsaramet

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Posted 17 August 2022 - 03:11 PM

Use telescopius.com to plan your session. Select by angular dimension, sort by brightness.

 

Dunno about SCT, but my newt is very collimation-sensitive. Needs to be done quite frequently. 

 

SCT has some disadvantages for learning. Biggest would be focal length. Second, guiding - at that focal length you need an off-axis guider. Then it's weight - I see it's about 11 kgs. Then it's speed - f10

 

So if you compare it with a short refractor, it will loose in all ways but one, and that's the narrower field of view useful to image smaller targets.

 

Of course, if your target is M31, the short refractor wins that way, too :)



#11 rrbailey89

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Posted 17 August 2022 - 03:27 PM

Use telescopius.com to plan your session. Select by angular dimension, sort by brightness.

Dunno about SCT, but my newt is very collimation-sensitive. Needs to be done quite frequently.

SCT has some disadvantages for learning. Biggest would be focal length. Second, guiding - at that focal length you need an off-axis guider. Then it's weight - I see it's about 11 kgs. Then it's speed - f10

So if you compare it with a short refractor, it will loose in all ways but one, and that's the narrower field of view useful to image smaller targets.

Of course, if your target is M31, the short refractor wins that way, too :)


Thanks for the link, I'm still very new to all this and trying to learn as much as possible. Can you explain what an off axis guider is/does or provide a link to one?

#12 gsaramet

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Posted 17 August 2022 - 03:53 PM

Normal guider is a second smaller scope with a modest camera which gives live images and is used for guiding. Now, the interesting part is the ratio of guidescope focal length vs main scope focal length. There is some math that can be done, there is no hard line (some guiding is generally better than no guiding). Different ratios are given, say 1:10. Now, a 200mm scope is not exactly small - which means costs, weight, flexure problems, so on.

 

So how do you guide a longer scope? You use a simple fact: the imaging circle covers more area than the sensor. So you can get a prism in the light cone, get some image out without affecting what gets on the main camera. Route that light to a guiding camera and voila! you have an off-axis guider. Looks like this: 

 

https://astrobackyar...ff-axis-guider/

 

You can of course google for OAG and get lots of links, examples and images ;)

 

Now, another way would be to put a secondary imaging chip on the main camera, near the edge of the imaging circle. 



#13 rrbailey89

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Posted 17 August 2022 - 04:39 PM

Normal guider is a second smaller scope with a modest camera which gives live images and is used for guiding. Now, the interesting part is the ratio of guidescope focal length vs main scope focal length. There is some math that can be done, there is no hard line (some guiding is generally better than no guiding). Different ratios are given, say 1:10. Now, a 200mm scope is not exactly small - which means costs, weight, flexure problems, so on.

 

So how do you guide a longer scope? You use a simple fact: the imaging circle covers more area than the sensor. So you can get a prism in the light cone, get some image out without affecting what gets on the main camera. Route that light to a guiding camera and voila! you have an off-axis guider. Looks like this: 

 

https://astrobackyar...ff-axis-guider/

 

You can of course google for OAG and get lots of links, examples and images wink.gif

 

Now, another way would be to put a secondary imaging chip on the main camera, near the edge of the imaging circle. 

Okay thanks for the explanation. My  wife and I actually started watching his channel a few weeks ago. From my understanding the EQ6-R Pro can hold a payload of up to 20kg (44lbs) and with my OTA that still leaves 30lbs of weight to play with. Is there any reason why I would want one type of guide camera/scope over another? In the future I plan to get a focal reducer to go to F6.3... or even double two of them up to get the OTA to attain what I understand to be about an F4. Im not sure if this matters when looking at guide cameras/scopes.



#14 Tapio

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Posted 17 August 2022 - 05:20 PM

I recommend OAG too even though it has its own quirks too (sometimes hard to find guide stars).
And I confess that I still use basic 50mm guide scope with my (reduced) C8.
By the way stacking reducers belongs to EAA territory where image quality is not so important.

Forgot the guide camera thing.
I use asi290mm. There are better and pricier ones.
So take your pick, but mono version is commonly preferred over color camera.

Edited by Tapio, 17 August 2022 - 05:23 PM.


#15 rrbailey89

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Posted 17 August 2022 - 05:22 PM

I recommend OAG too even though it has its own quirks too (sometimes hard to find guide stars).
And I confess that I still use basic 50mm guide scope with my (reduced) C8.
By the way stacking reducers belongs to EAA territory where image quality is not so important.

Thanks for the recommendation. Am I misunderstanding the research that I have been doing that states the guide camera should be half of the focal length of the telescope? OAG if I understand turns the camera into a replica of the focal length. 

 

Apologies for the potential EAA cross pollination. 



#16 idclimber

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Posted 17 August 2022 - 06:02 PM

I choose M31 simply because I needed to point it at something to get some practice. Is there something else in the same region of sky I could have used to get her potentially better results?

I am not using a reducer. Nor have I considered looking at collimation. The OTA is only a few months old and I think it's collimation is probably still good from the factory.

It sounds like I should look into guiding. Why is imaging with a refractor so much easier than with an SCT?

Thanks for the recommendation. Am I misunderstanding the research that I have been doing that states the guide camera should be half of the focal length of the telescope? OAG if I understand turns the camera into a replica of the focal length. 

 

Apologies for the potential EAA cross pollination. 

 

Subjects you can image primarily depends on your latitude and the time of year. 

 

It is extremely unlikely the collimation is ideal even on a new SCT other that the Edges. I have heard they can be pretty accurate out of the box. This is a basic skill for a SCT and eventually has to be learned to improve images. 

 

Guiding with an SCT needs to be done through an Off Axis Guider (OAG). Otherwise you will be chasing your tail with a guide scope. An OAG has the same focal length as the primary camera. 

 

Everything is harder on an SCT. I know this first hand comparing my 12" SCT and my 4" refractor. 

 

Your full frame Sony is another problem. Most scopes including the 8" SCT are not capable of imaging full frame. Once you correct the field with the f/6.3 reducer you will have severe vignetting. The refractors that support full frame are rare and expensive. Look up the price for a Takahashi FSQ-106EDX4. My Smaller 4" Stellarvue will barely do it a f/7. Pretty much any entry levels scope is the same problem. The only scope that comes close for a decent price is a Redcat. 


Edited by idclimber, 17 August 2022 - 06:03 PM.

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#17 rrbailey89

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Posted 17 August 2022 - 06:13 PM

Subjects you can image primarily depends on your latitude and the time of year.

It is extremely unlikely the collimation is ideal even on a new SCT other that the Edges. I have heard they can be pretty accurate out of the box. This is a basic skill for a SCT and eventually has to be learned to improve images.

Guiding with an SCT needs to be done through an Off Axis Guider (OAG). Otherwise you will be chasing your tail with a guide scope. An OAG has the same focal length as the primary camera.

Everything is harder on an SCT. I know this first hand comparing my 12" SCT and my 4" refractor.

Your full frame Sony is another problem. Most scopes including the 8" SCT are not capable of imaging full frame. Once you correct the field with the f/6.3 reducer you will have severe vignetting. The refractors that support full frame are rare and expensive. Look up the price for a Takahashi FSQ-106EDX4. My Smaller 4" Stellarvue will barely do it a f/7. Pretty much any entry levels scope is the same problem. The only scope that comes close for a decent price is a Redcat.


I do have an ASI178MC on the way that I ordered a few days ago. Do you have any recommendations for a good OAG setup to use with it?

#18 idclimber

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Posted 17 August 2022 - 08:07 PM

I do have an ASI178MC on the way that I ordered a few days ago. Do you have any recommendations for a good OAG setup to use with it?

My best suggestion is if you are purchasing for deep sky to stop. The 178mc is a planetary camera and suitable for that. The sensor is however very small, especially compared to your Sony.  If you want a camera that can do both consider the 533mc. I understand however it is a lot more money. 

 

The common OAG for an SCT is the Celestron unit. I prefer the ZWO OAG-L but that is better paired with the 2600mc. You will also need a guide camera and any old camera will not do. Either the 174mm mini or the 290mm mini is required. You likely will not get enough stars with the older 120mm mini. 

 

Again, to repeat getting this to work is both extremely hard and expensive. A much cheaper path is the refractor that Bob suggested. I would suggest a Redcat as you could use your Sony with that and you could even delay setting up the guide scope and guide camera as the shorter focal length will put less demand on your tracking. Also a 50mm guide scope and a 120mm would work perfectly with that combo. A guiding solution far cheaper than what is needed on the SCT. 


Edited by idclimber, 17 August 2022 - 08:08 PM.

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#19 rrbailey89

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Posted 17 August 2022 - 09:05 PM

My best suggestion is if you are purchasing for deep sky to stop. The 178mc is a planetary camera and suitable for that. The sensor is however very small, especially compared to your Sony.  If you want a camera that can do both consider the 533mc. I understand however it is a lot more money. 

 

The common OAG for an SCT is the Celestron unit. I prefer the ZWO OAG-L but that is better paired with the 2600mc. You will also need a guide camera and any old camera will not do. Either the 174mm mini or the 290mm mini is required. You likely will not get enough stars with the older 120mm mini. 

 

Again, to repeat getting this to work is both extremely hard and expensive. A much cheaper path is the refractor that Bob suggested. I would suggest a Redcat as you could use your Sony with that and you could even delay setting up the guide scope and guide camera as the shorter focal length will put less demand on your tracking. Also a 50mm guide scope and a 120mm would work perfectly with that combo. A guiding solution far cheaper than what is needed on the SCT. 

It was purchased with planetary at the forefront and DSO as a bonus. I assumed it would be okay for DSO (granted not the best) based off of how it appeared to compare against the other options available at ZWOs website. According to there website the 178mc scores pretty decently for DSO or at least I thought that it did.

 

Another reason I ultimately decided to get the 178mc was because I felt that I would have much more granular control over the camera than I would with the Sony because it seems Sony does not like other programs such as N.I.N.A to control its cameras. 

 

I ultimately landed on getting the ZWO OAG + 1.25″ Helical Focuser & ASI174MM Mini (mono) for guiding. 



#20 idclimber

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Posted 17 August 2022 - 09:35 PM

The ASI174mm is arguably the best guide camera available right now. The problem with pairing it with the standard ZWO OAG is the small prism in that model. As such the larger prism in the OAG-L is preferred and matches the camera. 

 

Here is a quick snapshot I took using TheSkyX and showing the relative field of view of the various cameras with the 8" SCT at f/6.3. The largest is the full frame, The second is the APS sized 2600, The square box shows the 533mc and lastly is the 178mc. 

 

The backdrop is Andromeda and shows the relative size. You can do the same with websites like telescopius.com and I recommend you do so.  

 

Screen Shot 2022-08-17 at 8.20.17 PM.jpg

 

 

 

 



#21 bobzeq25

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Posted 17 August 2022 - 09:46 PM

Okay thanks for the explanation. My  wife and I actually started watching his channel a few weeks ago. From my understanding the EQ6-R Pro can hold a payload of up to 20kg (44lbs) and with my OTA that still leaves 30lbs of weight to play with.

Weight is not the only thing that matters.  Focal length counts, a lot.  Weight can rule a setup out.  It can't rule one in.

 

No one would dream of trying to use two reducers.  Image quality would likely (almost certainly) be really awful.  An optical engineer designed the reducer.  He did not design one to be stacked.

 

This business is really unintuitive.  Two things work to help you fight through that.

 

Actual knowledge.

 

Following the crowd.  Standard practice is standard because it reflects the experience of many people.  "The wisdom of crowds" can really help you deal with the unintuitive nature.

 

It was purchased with planetary at the forefront and DSO as a bonus. I assumed it would be okay for DSO (granted not the best) based off of how it appeared to compare against the other options available at ZWOs website.

The question is (right now) not what is best for imaging.

 

It's what is best for _learning_ imaging.

 

Those are _often_ completely different things.  The ZWO website is talking about imaging.  Not about learning imaging.

 

Most everyone who does both planetary and DSO imaging uses two different cameras.  I certainly do.   For DSOs the most important things are low thermal noise and field of view.  For planetary, speed, you're shooting many frames per second.  No camera is really good at both.

 

Put all the above together.  An excellent camera for learning DSO imaging is the ZWO533MC PRO, cooled.
 


Edited by bobzeq25, 17 August 2022 - 09:52 PM.


#22 NorthJersey

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Posted 17 August 2022 - 09:49 PM

install nina 3 point alignment . It helped greatly. I had weird stars. My polar alignment i though was dead on. It was off a total of 12 degrees. Start with the basics first. Then work your way up thru the mount then focus, then iso. I would start there.



#23 idclimber

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Posted 17 August 2022 - 10:07 PM



install nina 3 point alignment . It helped greatly. I had weird stars. My polar alignment i though was dead on. It was off a total of 12 degrees. Start with the basics first. Then work your way up thru the mount then focus, then iso. I would start there.

Polar alignment may be difficult if he uses the 178mc with his SCT. The field of view may not provide enough stars to perform a plate solve. It was definitely an issue for me with my larger 12" scope when I only had the 224mc. If this is the case you will have to do a drift align. 

 

M31 was one of my first targets. I purchased and used the 4" refractor as suggested by people like Bob when I started this process 3 years ago. If you click on the image below it will take you to my Astrobin page where you can pull up the image in its full resolution. I have other images on the site including some from my 12" SCT.

 

Now given that I have both a 12" SCT and a 4" refractor and I have figured both out, I take most of my images with the refractor. I also have a 6" refractor being built. When that gets in I doubt I will image with the SCT much at all and may eventually sell it for something else. 

 

get.jpg?insecure


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#24 bobzeq25

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Posted 17 August 2022 - 10:37 PM

A 4 inch refractor? (above)  Gigantic scope.  Here's my Andromeda with a 70mm scope.  Reduced to F4.8, 336mm.  2.8 rompin stompin inches.  <smile>

 

https://www.astrobin.com/263253/J/

 

That's from my backyard.  Red Zone.  Bortle 7.  magnitude per arc second squared low 18s.

 

Understatement of the year.  Traditional DSO imaging is nothing at all like visual astronomy.  Visual instincts will send you up a _very_ bumpy road.


Edited by bobzeq25, 17 August 2022 - 10:40 PM.

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#25 rrbailey89

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Posted 17 August 2022 - 11:06 PM

Okay so will I be able to image anything with the 8SE and the 178MC/174MM ? Or is it that it will just be difficult?


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Also tagged with one or more of these keywords: Astrophotography, DSO, Imaging, Polar Alignment



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