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8SE Mount Advice

astrophotography imaging SCT eq dso dslr equipment cassegrain beginner
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#51 Jujubean

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Posted 13 April 2020 - 09:28 AM

M42 was my first deep sky target, and I got a few shots I’m really proud of. It’s not much, but it was amazing to see the nebula with only 15 seconds of exposure. 
 

CD4BA2C3 9735 4DF7 B604 15D32F630330
8668B528 0E87 415B 9BEC 8E74A9B3DD7E


#52 GuitsBoy

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Posted 13 April 2020 - 09:37 AM

M42 Was mine as well.  First night out with the telescope.  Didnt know what we'd really be able to see with it at the time.  Saw the fuzzy through the eyepiece and decided to give the camera a shot.  Tried my best to focus through the viewfinder, and clicked the shutter for a ten second exposure.  Not expecting to see much of anything at all, the image that showed up in display blew my mind. Me and my 5 year old son were instantly hooked.

 

I guess its everyone's favorite first DSO.  All these years of looking up at orion with my bare eyes, I never noticed that one fuzzy star.  Now I cant stop looking.



#53 Jujubean

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Posted 13 April 2020 - 10:36 AM

GuitsBoy,

 

I've watched a few videos on how to polar align the scope with the wedge. I saw I have to align the scope with Polaris... and apparently it shouldn't be centered? Where should Polaris be in a 25m eyepiece?

 

After aligning with Polaris, I'm supposed to align with two more stars just like w/out polar alignment, is this all correct? Thanks.



#54 GuitsBoy

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Posted 13 April 2020 - 11:13 AM

GuitsBoy,

 

I've watched a few videos on how to polar align the scope with the wedge. I saw I have to align the scope with Polaris... and apparently it shouldn't be centered? Where should Polaris be in a 25m eyepiece?

 

After aligning with Polaris, I'm supposed to align with two more stars just like w/out polar alignment, is this all correct? Thanks.

 

If I recall, you said your optimum spot for observing wont allow you to see polaris, right?   Thats fine.  Here's what I would do:

 

Set up  the scope and level it somewhere that you can see polaris, then straighten the OTA out and adjust the mount alt to get polaris in the center of the eyepiece. This will set your mounts alt adjustment.   Then bring your telescope to  the better viewing area and again level it.  The alt should be right on.  Rotate the telescope to where you think polaris should be, then start the eq-north alignment.  Pick a good first star that you have clear views to.  I usually use sirius as my first star.  Once the telescope slews to the star, rotate the tripod to get the star as close as you can, then finish up by using the controls as usual.  On the second star, just use the controls, dont rotate the tripod.  After that, you should be roughly aligned, but not perfect. 

 

Now, youll want to do whats called an ASPA (All Star Polar Align).  Basically go out to the root menu in the hand controller, then press align, and find mount align.  It will ask you to center a star with the controls, then it will slew away, and slew back to where the star would be if the mount were perfectly aligned.  This second time, youll adjust the mount / tripod to get the star centered, without using the hand controller.  Just follow the directions.  Once you complete  the ASPA, shut the mount off, turn back on, and do a final eq-north alignment.  Now you should be spot on.

 

If youre happy with the polar alignment, see if you can accurately mark the tripod legs so that you can quickly put the scope back in the exact same position.  Then the next time youll be able do a simple eq-north alignment and go without needing another ASPA.  In my case, I have one tripod leg against a crack in the curb of my cul-de-sac, and the second leg is indexed with a small nail I drove into  the asphalt to mark its location.  Now every time I go out, I put the legs in the right place and know the mount's polar alignment is good.

 

EDIT:  Just to touch on the issue of polarisi not being centered, thats true.  The north celestial pole is slightly off from polaris and changes as the earth rotates throughout the day, as well as throughout the year.  If I'm setting up in a different location, I typically use a phone app like google sky that shows the NCP as well as polaris, and I just make a mental note of where the NCP is in relation (eg. 10 o'clock from polaris)  then Ill aim the scope accordingly.  Its a bit of trial and error, but with a 32mm eyepiece, I was looking for about 10% the distance from the center to the edge of view.  Now I'm using a 15mm reticle eyepiece, and its probably closer to 30% off from the center.  Hope that makes sense.  Regardless, none of that will matter if you do the ASPA instead.  Polar aligning with the OTA is kind of a quick and dirty alignment method in my opinion, but works if you dont need to be perfect.


Edited by GuitsBoy, 13 April 2020 - 11:20 AM.


#55 rnyboy

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Posted 13 April 2020 - 12:09 PM

JJ and GB...  It seems like M42 is pretty much everybody's first DSO image.  Hard to beat really being big, bright, AND colorful.  The second time with live stacking I had an image more like Jujubean's bottom image with that additional area of nebulosity towards the top of his image showing up.  I think I was using 2 stacked f6/3 reducers that time but possibly it could have been one f/6.3 and the 0.5x.  I need to get more organized and do a better job of recording what I'm using in my optical train and the distances between reducers.

 

My scope is all set up to do some imaging with the f/6.3 and 0.5x reducer for f/3.2.  This time I have more "sensible" values for the reducer to sensor spacings and I hope the images have less distortions at the edge of the field than I had the first time I did this.  I should be able to have more than a full moon in my horizontal FOV and about 95% of the full moon in my vertical FOV for 0.84o x 0.48o.   There's a slim chance I could get to 1.3o x 0.76o with two stacked f/6.3s and the 0.5x reducer for an f/2 setup but I could easily run out of focus travel and even if enough focus I'll probably see some pretty severe vignetting and other image artifacts like coma.  It's all something of a game to see what I can image reasonably successfully at faster speeds and wider FOVs.  The big push and hope is to have a poor man's f/2 Hyperstar kind of setup for scope speed only with a much smaller FOV than Hyperstar would provide.  Having that 25x faster exposure and widest FOV one can get with a non-Hyperstar 6SE would be really sweet.

 

This is what I got for the super moon in March at more like f/4 (two stacked f/6.3s, 0.69o x 0.39o FOV)...

 

https://www.cloudyni...12949_45111.jpg

 

To add to what GB said about Polaris...  If you stick around for about 13,000 years the "north" star will probably be Vega.  Our north, and of course the south, celestial pole traces a circle in the sky every 26,000 years.  Those of us in the northern latitudes are just kind of lucky that Polaris is as close as it is to the pole axis right now and that we have that "north star".  People in the southern latitudes don't have it as easy for there south polar alignments because there is no bright object for them to point too (subject to change in the somewhat distant future I suppose).


Edited by rnyboy, 13 April 2020 - 12:39 PM.


#56 Jujubean

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Posted 13 April 2020 - 05:09 PM

rny and GB,

 

I'm going to try to polar align for the first time... Thanks for the advice GuitsBoy. Can I use CPWI to polar align and control my scope with the wedge on?

 

Nice moon photo rny, I have yet to photograph a supermoon, but hope to do it on the next one. The recent supermoon was too far in the trees for me to photograph, but it was pretty cool to look at. This is a photo I took a few days before the supermoon. I'm pretty happy with it as my first moon photo with a DSLR.

 

163FEC57 A81E 4E40 933E C4E0C68E47F5
 
Since my 8se is at 2032mm focal length, I couldn't capture the whole moon. I used photoshop to put together multiple photos.

Edited by Jujubean, 13 April 2020 - 05:12 PM.


#57 rnyboy

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Posted 14 April 2020 - 06:36 AM

Jujubean..  Nice image of the moon.  Same problem for me with my 385mc in that I can't capture the full moon even at f/3.2.  I've occasionally thought of trying to stitch together multiple images of the Andromeda galaxy.  It would take at least six images I think to get something so big with my ~1.5o max FOV but it could be a really cool image for a screen saver background.  I haven't used any type of stitching software for astro images yet.

 

I think CPWI allows for control with a wedge.  I think I've seen that it allows for equatorial tracking while working with my scope.  Could be wrong though, since I really haven't paid attention to that mode of operation since it doesn't apply to me.



#58 Jujubean

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Posted 14 April 2020 - 08:46 AM

rny and Guits,
Had some trouble aligning the wedge. I tried pointing towards Polaris but I couldn’t view it because I couldn’t put in an eyepiece because there was not enough room. I then looked at some videos, got confused, and tried again. I did solar system polar alignment with Venus, but it never prompted me to do anything with Polaris... confused1.gif

 

Thanks for your help!



#59 GuitsBoy

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Posted 14 April 2020 - 08:51 AM

Keep in mind, polar alignment means aligning to the north celestial pole, not aligning to polaris.  Polaris just happens to be conveniently close to the NCP.  In theory, you can use any stars to align to the NCP.  I only use polaris for my rough alignment before even powering the mount up.



#60 Jujubean

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Posted 14 April 2020 - 07:10 PM

Okay...
 

I’m still a bit confused. I align to the first star, then I align to the second star. Is that all I have to do? I thought I had to adjust the wedge or something?

 

Thanks for the help!


Edited by Jujubean, 14 April 2020 - 07:10 PM.


#61 GuitsBoy

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Posted 15 April 2020 - 10:32 AM

Okay...
 

I’m still a bit confused. I align to the first star, then I align to the second star. Is that all I have to do? I thought I had to adjust the wedge or something?

 

Thanks for the help!

Think of it as two separate things that need alignment:

 

1. The wedge needs to be polar aligned to match the rotation of the earth

2. The mount needs to be aligned to stars so it knows how its oriented so that go-to works accurately.

 

Unfortunately, since we dont have a polar scope, we have to do this in three parts.  Basically, you do number 2 first.  Go back and do number 1.  Then finalize with number 2 again.

 

You start by setting up the scope and just try to get it pointed generally in the right direction.  Do an EQ-north alignment.  This will get your go-to somewhat close, but not quite perfect since youre not accurately polar aligned.

 

Go back and do an "All Star Polar Alignment" (or mount align) which will help you polar align your wedge, even if you cant see polaris.

 

Lastly, shut the scope down and power back on.  Do a final EQ-north align (for your go-to) since the wedge is now polar aligned. 



#62 GuitsBoy

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Posted 16 April 2020 - 12:14 PM

Jujubean, did you have any luck, or didn't get out again yet?

I got out last night and had some mixed luck with 60 second guided exposures.  Probably 60% were stackable, and ultimately probably only 30-40% were used.  Still dialing in the mount.  Theres so much slop in the declination axis I get overshoot, and if I tone the agressiveness down, its not enough to keep the star.  Need more practice, but shows some promise. I still may go back to just higher numbers of stacked 20" subs.

 

cumulative_m51_20200416 (Small).jpg
M51

 

cumulative_m81-m82_20200416 (Small).jpg

M81+M82
 

2020-04-15_m1 (Small).jpg

M1 - the Cra*P* Nebula.  This one is hard to get any detail to resolve.


Edited by GuitsBoy, 16 April 2020 - 01:03 PM.

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#63 Jujubean

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Posted 17 April 2020 - 03:47 PM

Didn't get much last night... had trouble aligning the wedge. I tried to align it for about 30 minutes until I gave up and used alt-az mode.

 

I tried with and without CPWI, neither of which worked. I tried multiple alignment options but none worked. I have a terrible view of the north, so it is very hard to get an alignment...

 

I'm not sure if the wedge is worth it. Even if I do get it to work, I'd hate having to take so long to setup and polar align. I'm thinking of maybe getting a hyperstar.

 

Anyways, I'll keep trying. I'll tell you if i get it to work.



#64 rnyboy

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Posted 17 April 2020 - 04:58 PM

Hyperstar is really cool, but kind of expensive, plus I think you'd want a higher resolution cmos sensor made for astrophotography at the front, so maybe have to figure in that expense as well.  Plus a C8 on an SE mount for Hyperstar may not be the best idea but the much shorter exposures will certainly help in that respect.  On that I can't help with any data or experience.   If I had a C8 like you instead of my C6, and on a better mount, I'd probably think more about adding a Hyperstar too.  You can do quite a bit though with stacked reducers.  Plus you don't have to somewhat dedicate your scope to being a Hyperstar instrument.  I mean sure, you can remove the Hyperstar, replace the mirror, recollimate the scope, and then use it like a regular scope.   But I have to imagine that's something of a pain to switch back and forth.  But for speed and FOV I can't think of anything that beats Hyperstar unless it's a new scope dedicated to wide field DSOs.

 

There's a certain amount of trying to make a silk purse out of a sow's ear when you're dealing with the limitations of the SE mounts and pushing too far could become both expensive and frustrating such that a better mount is the better option.


Edited by rnyboy, 17 April 2020 - 05:05 PM.


#65 Jujubean

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Posted 17 April 2020 - 05:18 PM

I'm considering the hyperstar because it will allow me to take exposures much quicker, as you said. I know it is expensive, but it's f/2...

 

I know the SE Mount isn't great, but its quick and portable. Polar mounts take a lot of time to get a good alignment, and I can't see Polaris from my location which complicates Polar alignment even more. I'm only going to be taking <30s exposures, so it should be fine for that, right?

 

Reducers have chromatic aberration, vignetting, etc. Does this also affect the image quality with the Hyperstar?

 

For now, I'm fine with my DSLR.


Edited by Jujubean, 17 April 2020 - 05:27 PM.


#66 rnyboy

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Posted 18 April 2020 - 07:22 AM

Not an expert on Hyperstar but should be no vignetting because the vignetting one sees with too much reduction is due to the SCT center baffle which is only used if you have the secondary mirror in place.  The baffle is the limiting element for the classic SCTs.  Chromatic aberrations are something of a subjective property.  Some people can't stand any and other's are OK with it.  For me the SCTs are not objectionable and are pretty much designed to be CA free.  Most inexpensive glass lenses are going add some degree of CA depending on the setup and, yes, multiple reducers can add to that.  But it's also offset some by the larger FOV imaged when they are used.  In my opinion you can get more CA from density variations in the atmosphere when going from the horizon to the zenith then is native to an SCT.  In fact there are compensators for CA free apo refractors to help correct for atmospheric CA.

 

There are tons of Hyperstar images, if taken on a C8 and you really like them then go for it.  But check to see what information is provided with the images to get an idea on how much mount properties affect the image.  But all things considered as an addition to your current setup Hyperstar is the best you will currently get as far as having the fastest exposures, widest FOVs, and least amount of CA.

 

If you are really critical about the images you want then it's possible you may be most satisfied by going to a dedicated DSO/DSLR setup.  Some aren't all that expensive and you'd have the 8SE for planetary/small object imaging.  Or a fast Newtonian?

 

One thing to remember is the larger the camera you use for imaging with Hyperstar the larger the central obstruction is going to be, so you effectively have less aperture and more reduction in contrast.  Compare the outside area of your DSLR vs a dedicated CMOS imager and I think the DSLR is about 2x more area so you've lost some aperture, meaning it's effectively not f/2 but maybe more like f/2.5 - 3.  Everything is a compromise.


Edited by rnyboy, 18 April 2020 - 07:41 AM.


#67 Noah4x4

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Posted 18 April 2020 - 08:25 AM

I use Hyperstar with a camera that has a perfect narrow barrel to suit it (Atik Horizon). The obstruction on an 8" is no greater than the SCT's regular secondary mirror.

 

The big advantage is that at f/2 images form 25x faster than at f/10. This permits shorter exposures and shorter total integration time. I need no wedge, polar alignment or guiding. Removing secondary mirror also increases FOV x5.

 

That last advantage is also a weakness as it means a corresponding reduction in magnification. This is where 4K UHD resolution, large sensor and small pixels are an advantage as you will want to use deeper camera zoom.

 

Frankly, I love Hyperstar because it allows me to cheat. I will never win Astrophotographer of the Year as I have zero patience. But I can have a recognisable Horsehead on screen in about five seconds. Quality images take a little longer, but not the hours required at f/6.3 or f/10.


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#68 Jujubean

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Posted 18 April 2020 - 09:40 AM

Noah,

 

It seems you really like your hyperstar with the stock 8se. Can I see some images you have taken?

 

I will upgrade to a CMOS or CCD camera in the future, but for now I'm going to use my DSLR. Even with the large DSLR, it will still be a massive improvement from f/10.


Edited by Jujubean, 18 April 2020 - 09:54 AM.


#69 sandconp

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Posted 18 April 2020 - 01:46 PM

I use Hyperstar with a camera that has a perfect narrow barrel to suit it (Atik Horizon). The obstruction on an 8" is no greater than the SCT's regular secondary mirror.

 

The big advantage is that at f/2 images form 25x faster than at f/10. This permits shorter exposures and shorter total integration time. I need no wedge, polar alignment or guiding. Removing secondary mirror also increases FOV x5.

 

That last advantage is also a weakness as it means a corresponding reduction in magnification. This is where 4K UHD resolution, large sensor and small pixels are an advantage as you will want to use deeper camera zoom.

 

Frankly, I love Hyperstar because it allows me to cheat. I will never win Astrophotographer of the Year as I have zero patience. But I can have a recognisable Horsehead on screen in about five seconds. Quality images take a little longer, but not the hours required at f/6.3 or f/10.

I second that 



#70 Noah4x4

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Posted 18 April 2020 - 03:17 PM

Noah,

 

It seems you really like your hyperstar with the stock 8se. Can I see some images you have taken?

 

I will upgrade to a CMOS or CCD camera in the future, but for now I'm going to use my DSLR. Even with the large DSLR, it will still be a massive improvement from f/10.

I think you slightly misunderstand what I do with camera and Hyperstar. I don't routinely save any images as I am not seeking to produce Astro-Art....

 

1. I am an EAA Observer and not an EAA Imager.

 

2. The reason that I take this route is because of extreme local light pollution. Visual astronomy is now impossible at my location.

 

 

3. I don't seek to compete with those that want to win Astrophotographer of the year. If there are a few hot pixels and a bit of vignetting I don't care.

 

4. It is almost impossible to demonstrate in Cloudy Nights how something looks on 4K UHD monitor when the reader is using a 1080p display and Cloudy Nights limits image size etc.

 

 

However, simply to give you an idea, below is a phone camera photograph of the (near) 'Live' view of the Horsehead as it is being actually VIEWED live on my 4K UHD monitor indoors over wireless. Whilst not the greatest image in an artisic sense, this taken was on my first light merely ten minutes after first connecting camera and Hyperstar.  The crucial point is I can consistetly reproduce this level of detail of this reputed challenging object in about three x 5 second stacks using Hyperstar. It would take 25x longer to pull out this level of detail if not on Hyperstar at f/2. You will perhaps understand now about when I talk about (near) live observing rather than imaging.

 

Here, do please ignore the fact that my stars are imperfect  as I needed to tweak FWHM and collimation etc and there is some distortion caused by the angle of my phone camera and reflected light. Concentrate simply upon the level of nebula detail extracted in a (near) live paradigm in merely a few seconds total integration time. Yes, If I had allowed this to run on to have a total integration time of perhaps ten to twenty minutes then I would be chasing astro-art perfection. But this is simply a demonstration of (near) live observing at my FIRST LIGHT with Hyperstar. If you want to see what can be done in an astrophotography paradigm, visit the experts at https://starizona.co...perstar-images/ Also take a look at the Starizona videos on YouTube.

 

Horsehead.jpg

 

This second somewhat better image (M51) demonstrates the huge field of view with Hyperstar and why high resolution and camera zoom is desirable. This image is merely 49 x 7 seconds, hence around five minutes. Sky conditions Bortle Six Seeing was pretty ghastly through whispy cloud. I think this again illustrates what can be acheived in very short time at f/2 and the 'Buck Rogers' feel of the huge FOV on Hyperstar. Again, I could have worked harder on FWHM, but as I said, I am an observer and have little interest in photography. Here, I stress I am using merely 7 second exposures. If you compare with the guided 60 second exposures in post #62 then those are inevitaby better. But imagine what I could do at 60 seconds on the right mount with guiding, and polar alignment. Here, I am using alt-az, no guiding, no polar alignment, no wedge/gem. No frustration, no need for patience over hours of waiting for images to form (I have none).

 

Whirlpool 49x7s stacks = 735s.jpg


Edited by Noah4x4, 18 April 2020 - 03:38 PM.


#71 Jujubean

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Posted 19 April 2020 - 08:51 PM

Thanks for all your responses, you guys have been very helpful! waytogo.gif

 

As a beginner looking to taking a few quick shots of the cosmos, I think the Hyperstar is the best option for me. The polar alignment process is not for me, atleast not with the wedge. I think I'll be purchasing the Hyperstar, but before I do, may I ask if anybody thinks I should go with something else?

 

Thanks again for your help.




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