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9.25 SCT, it ain't no planet scope

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#276 Redbetter

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Posted 09 November 2018 - 10:27 AM

Not IME.  IMO what you are experiencing is the misnomer that aperture rules. 

You might want to read the thread before pushing misinformed bias.   The scope was shipped from Louisiana to Ohio over a year ago and the OP had not even checked the collimation. 


 

#277 Asbytec

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Posted 09 November 2018 - 10:30 AM

I usually start observing without checking collimation unless the scope has been for a ride in the car since the last time I used it. If the stars look off after the scope has had time to cool down, then I check collimation. If the stars look okay, I just keep observing.

Sure. Point being to ensure it's well collimated. Whenever we chose to do it.

As Bill said above, SCTs really need to be prepped for observing. Some form of thermal management and good collimation. Factors we can influence and make a difference.

Aperture itself increases contrast over small angular distances. It's called resolution.

Edited by Asbytec, 09 November 2018 - 10:32 AM.

 

#278 Sarkikos

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Posted 09 November 2018 - 10:40 AM

Larger aperture done well will always outperform smaller aperture.  The trick is to do the larger aperture well.  

 

Often it's easier to just take out a good, smaller aperture refractor.  grin.gif

 

Mike


Edited by Sarkikos, 09 November 2018 - 02:42 PM.

 

#279 Bomber Bob

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Posted 09 November 2018 - 10:48 AM

Often it's easier to just take out a good, smaller aperture refractor.

 

So true...  Vixen :: Vixen...

 

Vixen FL80S S13.jpg VMC200L S05- EM-1S Mount.jpg


 

#280 CHASLX200

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Posted 09 November 2018 - 10:50 AM

A well built Newt does all i need it to do.


 

#281 Chris Johnson

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Posted 09 November 2018 - 11:37 AM

Regarding point 12 of your post, the selection of stars on the east or west for alignment can be changed by pressing the Menu” button before selecting an alignment star. Pressing the menu button cycles between E, W or no preference. This is covered on page 15 in the AVX manual.


 

#282 Jaimo!

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Posted 09 November 2018 - 11:53 AM

Okay, the set up steps are as follows:
1. put on boots and warm pants if winter and put the scope outside.
2. make sure the one spot in the yard where I can see the southern horizon and Polaris isn't soggy.
3. spray Yard Gard if summer.
4. open garage and carry AVX to observing spot. Put in approx. right position since Polaris is not yet visible.
5. Load EP case, counterweights, battery, EP case stand, radio, wires, dew shield, and controller onto wheelbarrow.
6. Push wheelbarrow to backyard.
7. return to garage for observing chair.
8. wait for darkness
9. align polar scope, then add weights.
10. go get scope.
11. attach scope, dewshield, balance scope, attach wires and controller.
12. Align mount, a process made difficult by all the trees to the immediate west. (The AVX insists on using western stars).
13. Go put on warm coat and hat, turn off lights.
14. Begin observing.
It takes more than a few minutes. Plus, I have to leave time to bring all that stuff back in.

I does not sound like you enjoy astronomy...  Getting dressed and moving equipment is all part of the gig.

 

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#283 Sarkikos

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Posted 09 November 2018 - 12:04 PM

You have to get dressed and move equipment for most anything you do.

 

Mike


 

#284 gfstallin

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Posted 09 November 2018 - 12:10 PM

Okay, the set up steps are as follows:
1. put on boots and warm pants if winter and put the scope outside.
2. make sure the one spot in the yard where I can see the southern horizon and Polaris isn't soggy.
3. spray Yard Gard if summer.
4. open garage and carry AVX to observing spot. Put in approx. right position since Polaris is not yet visible.
5. Load EP case, counterweights, battery, EP case stand, radio, wires, dew shield, and controller onto wheelbarrow.
6. Push wheelbarrow to backyard.
7. return to garage for observing chair.
8. wait for darkness
9. align polar scope, then add weights.
10. go get scope.
11. attach scope, dewshield, balance scope, attach wires and controller.
12. Align mount, a process made difficult by all the trees to the immediate west. (The AVX insists on using western stars).
13. Go put on warm coat and hat, turn off lights.
14. Begin observing.
It takes more than a few minutes. Plus, I have to leave time to bring all that stuff back in.

If your C9.25 is like mine, horizontal collimation and vertical collimation should be the practically the same. This is true for both my C8 and C9.25 (the C11 is too large for collimation to hold between horizontal and vertical viewing). This makes it easy to collimate on an artificial star during the daytime or a cloudy night. You'll want to tweak it on a real star at some point 

 

I totally hear you about setup and tear down times. I'm not in school, but even just quick observing nights are 30 minutes to set up - a vast improvement over last year's time, which included carting the entire setup up to 1/2 mile each way- and 20 minutes to take down. 

 

George


 

#285 BillP

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Posted 09 November 2018 - 12:35 PM

You might want to read the thread before pushing misinformed bias.   The scope was shipped from Louisiana to Ohio over a year ago and the OP had not even checked the collimation. 

 

Not misinformed, very much not bias but 50 years of experience with scopes, and matters not relative to shipping and timeframe.  All the advice I gave is pertinent to all situations, i.e., knowing what management of one's scope is needed, buying from flexible sources, etc., etc.  Not sure what you are bringing to the thread based on this comment other than a bad attitude. lol.gif


Edited by BillP, 09 November 2018 - 12:40 PM.

 

#286 Deep13

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Posted 09 November 2018 - 02:21 PM

Deep, I can't help with some of the items in your preparation list related to weather and the specifics of your observing location, although you don't need to precisely polar align the scope. You can save considerable time by just lining up the RA axis with approximate true north. Just eyeball it. Stars will drift, but this won't affect collimation. Just keep recentering with the hand controller. You could also consider setting up your tripod and mount in your yard in a somewhat fixed location, polar aligning it precisely one time, and then keeping it there and just remove the scope and cover the mount with a tarp when you are done. Then setup will be a breeze next time. The reason your post has generated nearly 9000 views and 11 pages of responses is not because of what you said in your original post describing difficulties with the scope. It was the title of your post which people objected to. You made a firm statement that a scope was not good for planets, despite the fact that many people all over the world have great success with the very same scope. If you had phrased your post as a simple question about how to maximize performance of your scope, this post would have generated very little emotion, and probably would have ended after a page or two stating the need to collimate the scope.


Already explained the title.
 

#287 CHASLX200

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Posted 09 November 2018 - 02:32 PM

Not misinformed, very much not bias but 50 years of experience with scopes, and matters not relative to shipping and timeframe.  All the advice I gave is pertinent to all situations, i.e., knowing what management of one's scope is needed, buying from flexible sources, etc., etc.  Not sure what you are bringing to the thread based on this comment other than a bad attitude. lol.gif

We have a few here that can't get it in their head that not all SCT's are perfect


 

#288 Deep13

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Posted 09 November 2018 - 02:40 PM

Okay, I am going to make an artificial star with a flashlight and some aluminum foil. And it won't take long to collimate. Unfortunately, I won't know if it will fix the problem until I can observe with it. Maybe get a brief window to observe around New Year, otherwise, it's not going to happen until May.

Edited by Deep13, 09 November 2018 - 03:22 PM.

 

#289 Sarkikos

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Posted 09 November 2018 - 02:41 PM

We have a few here that can't get it in their head that not all SCT's are perfect

No SCT's are perfect!

 

:grin:

Mike


 

#290 CHASLX200

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Posted 09 November 2018 - 02:46 PM

No SCT's are perfect!

 

grin.gif

Mike

But a few here get upset when i tell it like it is.  5 out of around 60 SCT's i have owned i would call super and the rest were bad or lack luster.  So not a good avg.


Edited by CHASLX200, 09 November 2018 - 02:48 PM.

 

#291 Axunator

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Posted 09 November 2018 - 03:03 PM

No SCT's are perfect!

No actual physically existing scope is perfect. Yet every single one benefits from being collimated, and deserves to be before being condemned...


 

#292 punk35

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Posted 09 November 2018 - 03:39 PM

Every scope I own is a perfect scope including my sct. After all, they all show me celestial objects that seem pleasing to me despite any flaws the optics may introduce. Maybe I’ve never looked through a horrible scope, or an excellent one, but every scope I’ve owned is perfect for its primary role: enabling me to enjoy this hobby. 

 

If i ever get so stuck up that nothing but a perfect optic is good enough and the rest are trash, then just drop a 42” dob on melol.gif

 

I know we are all pretty serious about our equipment, but in the end it’s about enjoying a pastime. Even a crappy planetary scope might be a good deep sky scope. 


 

#293 WadeH237

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Posted 09 November 2018 - 04:17 PM

Deep, I can't help with some of the items in your preparation list related to weather and the specifics of your observing location, although you don't need to precisely polar align the scope.

 

<snipped alternate setup steps>  

I don't know about you guys, but I typically set up a scope when I am planning on observing with it.

 

I'm fully capable of setting most of my scopes up pretty quickly when I want to, but if I'm not planning on actually observing, I do have other things that I can spend my time on.  Case in point, one of my AVX mounts has a simple mechanical issue.  I've looked closely at the mount, and read a number of accounts of others, and I know exactly what I need to do - and it's not difficult.  But I don't have plans for that mount until next spring, so even though I could fix it without even taking it out of the house, there are too many other things that could use my time and attention right now.

 

It seems clear that the OP knows that he needs to collimate the scope, but it also seems strange to criticize him for prioritizing his academic activities over messing with a scope that he won't use until next year.


 

#294 Ron359

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Posted 09 November 2018 - 04:32 PM

We have a few here that can't get it in their head that not all SCT's are perfect

Still waiting for the "stacks of data" that proves they're all bad too.  gramps.gif  blahblah.gif blahblah.gif blahblah.gif


 

#295 Asbytec

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Posted 09 November 2018 - 05:07 PM

A well built Newt does all i need it to do.

And that is the point, isn't it? No scope is perfect, but a good one will do what we want it to do. Some will so it better. In order to do what we want it to do, or what it can do, some designs need some TLC. All scopes, even refractors, need to be thermally stable and should be collimated. The SCTs folded light path and internal mirror make it more so, and the design thankfully offers an easy means to collimate it. A scope needs to be given a fighting chance to perform, then we hope for good seeing. Yes, the obstruction has an effect of reducing contrast to some degree on small scales, but increased aperture improves contrast on those same small scales. The observer is part of the wobbly stack, too. We have to learn to garner what we can from the image given everything else. When it all comes together, scopes can do what we want them to do when given the chance. 


 

#296 Deep13

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Posted 09 November 2018 - 05:28 PM

You might want to read the thread before pushing misinformed bias.   The scope was shipped from Louisiana to Ohio over a year ago and the OP had not even checked the collimation. 

I did check it, I only found out from this thread that I was doing it wrong. When I defocused a star, the central dark spot was centered. That's how one checks a Newt or a refractor, but I now know there is more to it for a SCT.


 

#297 Asbytec

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Posted 09 November 2018 - 05:54 PM

When I defocused a star, the central dark spot was centered. 

Deep, yes, the dark spot (secondary shadow I presume) should appear to be centered. As Mike and I were discussing above, that's close collimation. But, I assert it's not sufficient. When you center the secondary shadow in the large donut, it's really more of a mechanical alignment showing the secondary itself looks centered in the light cone. For optical alignment, we really want to use the diffraction pattern itself right down the the Poisson spot and a few rings. To do that we have to be closer to focus well before the shadow is visible. Collimation is much more accurate when we center everything on the small diffraction artifact rather than shadows. Whether indoors with an artificial star, on the garage using a glint of sunlight, or outside with a star, get as close to focus as possible to see the central Poisson spot and a few diffraction rings. Again, I have seen instructions (and user images) that show a huge donut and shadow. That's close (mechanical), but not accurate (optical) alignment. 


 

#298 Deep13

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Posted 09 November 2018 - 05:55 PM

Okay, to summarize:

 

1. Planet views look smudged every time I went out. The few times I used the 5" refractor or 8" Dob, everything was sharp.

2. Defocused image was concentric, believed that meant the collimation was good.

3. Apparently, that's not enough to check for good collimation.

4. Also, likely still having thermal problems.

5. SCTs are lousy planet scopes, also SCTs are great planet scopes.

6. SCTs are really good with photos, which predicts their visual performance. Also, photographic ability is irrelevant to visual performance.

7. Some samples of a SCT models are better than others--an allowance I will not concede. (QC is the manufacturer's responsibility, not mine).

8. Test results something something Rochi Strehl something something.

9. People seem to think that I owe Celestron a degree of deference. I don't. My subject title is all singular (not 9.25s, not "they ain't..."). I said nothing about the whole line of 9.25s. I really don't feel I should have to explain plain language to people who are somehow offended by a criticism of hobby equipment. On the other hand, I had no reason to think mine was not representative. And if it has a defect that is atypical of the line, that's still on Celestron. (Note the use of the conditional "if.")
10. I will collimate it and test it on the moon, Uranus, and whatever else is out before selling it to make sure I don't sell someone a lemon, because ethics. Honestly, it looks good on DSOs as it is.


 

#299 CHASLX200

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Posted 09 November 2018 - 06:01 PM

Still waiting for the "stacks of data" that proves they're all bad too.  gramps.gif  blahblah.gif blahblah.gif blahblah.gif

And here you are saying i said they are all bad when i just said 5 i owned were super. Mos really don't know better until you have owned the scopes i have and have my kind of seeing.


Edited by CHASLX200, 09 November 2018 - 06:06 PM.

 

#300 CHASLX200

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Posted 09 November 2018 - 06:05 PM

And that is the point, isn't it? No scope is perfect, but a good one will do what we want it to do. Some will so it better. In order to do what we want it to do, or what it can do, some designs need some TLC. All scopes, even refractors, need to be thermally stable and should be collimated. The SCTs folded light path and internal mirror make it more so, and the design thankfully offers an easy means to collimate it. A scope needs to be given a fighting chance to perform, then we hope for good seeing. Yes, the obstruction has an effect of reducing contrast to some degree on small scales, but increased aperture improves contrast on those same small scales. The observer is part of the wobbly stack, too. We have to learn to garner what we can from the image given everything else. When it all comes together, scopes can do what we want them to do when given the chance. 

Every kind of scope has it good and bad points. APO's cost too much per inch, get heavy in the bigger sizes 7" and up and need a monster pricey mount.  Bigger EQ Newts are heavy in the 10" sizes and up. They need more collimation than SCT's and APO's.  But price per inch they can't be beat for planet work if you got the seeing.  SCT's are great for being smaller and lighter vs the same size APO and Newts.  So no matter what scope you pick other kinds of scopes do some things better.


 


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