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Newbie with a Dobsonian looking for eyepiece help (+more)

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#51 Don H

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Posted 16 September 2021 - 01:54 PM

That's an interesting point. I had hoped light pollution wouldn't completely rule out deep sky for me - do you think I can still see some objects, or is it time for me to be disappointed? And if not with a 2", is there another category of eyepiece that would be ideal for that?

 

The X-Cel LX is the model of Barlow I have, I hadn't looked at the EPs. Antares EPs seem like they would be good value for money. However if I'm better off with a 1.25" for whatever DSOs I can see here, it seems like it'd be wiser to get a 7-21 zoom - I'd have good magnifications for DSOs and planets all in one eyepiece. That doesn't quite get me to zero fuss, but it would be less than if I also had to exchange eyepieces. I'm actually kind of surprised you don't like zooms in that context - what is it you don't like about them, just the smaller FOV? Is it that big of a drawback?

 

I like your peep tube solution. Very simple and elegant waytogo.gif Will fashion one of those for myself. Unlike a dot sight, it won't eat coin cells.

Light pollution will diminish the view of some things more than others. Galaxies are probably affected the most, as well as extended nebulae and things like supernova remnants (like the Veil). You can still see the cores of many galaxies, but their structure and outer reaches are greatly diminished or gone in the muck. You can try to keep your exit pupil and sky background brightness down by using eyepieces at 25mm and below. I think using your stock 25 for a while will give you a good feel for how much DSO detail you can get. This would be most evident if you were able to look at the same object at home and under a darker sky some other night. An 18 or 20mm wide field ep could be even better for a bit more detail and contrast from home and at a darker sky location.

 

There are some objects that hold up better in LP. Globular clusters and open clusters can look good, especially at higher powers, like 80 -120x or even a bit more in your 8". Many planetary nebula can also show a bit of detail or even some color, like the Ring, Cat's Eye, Dumbbell and more. And the brightest show piece emission nebulae, like Orion, the Lagoon and the Swan will yield some structure, too. A filter might help a bit on nebulae. 

 

The small fov is definitely one thing I do not like about zooms. The other is having to turn the barrel to adjust power, which as Tony already mentioned, is a bit more fuss while wearing gloves. I prefer to just get a specific mag and larger fov by simply placing the ep in the focuser. 


Edited by Don H, 16 September 2021 - 01:58 PM.

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#52 Tony Flanders

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Posted 16 September 2021 - 02:06 PM

I agree that there's worse things, sure, but I'm not gonna ignore one problem just because it's overshadowed. Like I said, the fact that fiddling with eyepiece stuff is a problem for me isn't really up for debate here. Just whether there's a solution, and how comprehensive it is.
 
Interesting that zooms have such resistance! I'd have thought they'd be fairly light and easy to adjust. That is good to know.


They vary greatly, and the one I've had longest has gotten worse with age. But adjusting a zoom is best done with two hands, whereas changing eyepieces is strictly a one-hand job.
 
Filters are the worst; they're tricky to tricky to get in and out of storage and tricky to screw in, even without gloves. Once you're used to the set-screws they should be zero problem. As with most manual tasks, practice makes perfect.
 
I wear open-palm mittens, enabling me to do most delicate chores using my bare fingertips. (Changing eyepieces is not one of those chores; I can do it easily through my mittens.) I have never had problems with my fingers freezing to metal; I assume that happens only far below 0F. But people who worry about it wear thin liner gloves under their mittens.


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#53 Leaf

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Posted 16 September 2021 - 07:06 PM

Light pollution will diminish the view of some things more than others. Galaxies are probably affected the most, as well as extended nebulae and things like supernova remnants (like the Veil). You can still see the cores of many galaxies, but their structure and outer reaches are greatly diminished or gone in the muck. You can try to keep your exit pupil and sky background brightness down by using eyepieces at 25mm and below. I think using your stock 25 for a while will give you a good feel for how much DSO detail you can get. This would be most evident if you were able to look at the same object at home and under a darker sky some other night. An 18 or 20mm wide field ep could be even better for a bit more detail and contrast from home and at a darker sky location.

 

There are some objects that hold up better in LP. Globular clusters and open clusters can look good, especially at higher powers, like 80 -120x or even a bit more in your 8". Many planetary nebula can also show a bit of detail or even some color, like the Ring, Cat's Eye, Dumbbell and more. And the brightest show piece emission nebulae, like Orion, the Lagoon and the Swan will yield some structure, too. A filter might help a bit on nebulae. 

 

The small fov is definitely one thing I do not like about zooms. The other is having to turn the barrel to adjust power, which as Tony already mentioned, is a bit more fuss while wearing gloves. I prefer to just get a specific mag and larger fov by simply placing the ep in the focuser. 

Thank you for the information, I will look for these DSOs next time I get a clear night waytogo.gif How helpful are filters in bringing these things out? Will they be a worthwhile investment for me in the future?

 

I've noticed some red and blue fringing on either side of objects I view through the scope, particularly planets, a bit like watching those old bi-colour 3D films without the glasses. It looks like chromatic aberration but I was under the impression that reflector telescopes weren't susceptible to that. What do?



#54 Dave Mitsky

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Posted 16 September 2021 - 08:38 PM

I've noticed some red and blue fringing on either side of objects I view through the scope, particularly planets, a bit like watching those old bi-colour 3D films without the glasses. It looks like chromatic aberration but I was under the impression that reflector telescopes weren't susceptible to that. What do?

Those colors are due to atmospheric prismatic dispersion, which bright objects display when they are very low in altitude.

https://astropix.com...dispersion.html

 

https://astropix.com...serving/vd.html

 

https://cseligman.co...cdispersion.htm

 

https://www.youtube....h?v=YApeWCQT8OQ


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#55 Dave Mitsky

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Posted 16 September 2021 - 08:44 PM

Here's a photo of Venus that I took some time ago through the Naylor Observatory's 17" f/15 classical Cassegrain that shows the effects of atmospheric prismatic dispersion.

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  • Venus 17-inch Prismatic Dispersion Enlarged 600 CN.jpg

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#56 Leaf

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Posted 16 September 2021 - 08:54 PM

Those colors are due to atmospheric prismatic dispersion, which bright objects display when they are very low in altitude.

 

https://www.youtube....h?v=YApeWCQT8OQ

Gotcha, thanks. I was worried it might have been something wrong with the telescope or eyepieces. Just have to wait for them to be higher up in the sky. Gonna be a fun winter grin.gif

 

Since I didn't have anything better to do, I lubed the mount on my telescope, both the altitude and azimuth axes, so it slides waaayyy smoother and easier now. Almost feather-light on the altitude. Azimuth is still a bit sticky but glides easy once it's moving. I'm kind of amazed just how simple the Dobsonian mount is, having taken it apart and put it back together. Very smart design.



#57 PKDfan

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Posted 16 September 2021 - 09:35 PM

Hi Leaf! Having used a C8 with reducer at Grouse mountain in Vancouver, a 12mm 82° or greater apparent field eyepiece should make all of the Messier list objects sparkle, a ~2mm exit pupil and ~100×.

It will be a most used eyepiece.

Thats my best recommendation for a most useful eyepiece for a reflector user of your size and focal length.

Saanich or the area near has the 72" Dominion Astrophysical Observatory so seeing will be excellent more often than not, I would think.
Are you close to that?

I hardly ever saw the stars twinkle much, when I worked there for a few months during summer, when I was much younger.

Go slow and train your brain to exert every last scrap of information when observing the planets so that when they become more favourably placed you will be rewarded with great joy and happiness as you unlock previously hidden details.

For me, every time out when I first got the C8 was a greater and greater need to see as much as possible so I learned to slow down and OBSERVE every object I found.

More and more information was transfered/assimilated, its as if I added aperture to the scope.

Now with that experience under my belt, using my 4" apo is very rewarding as I believe I am utilizing every last millimeter of aperture I have.

Last thought, parroting others, buy once cry once.
Quality costs!


Clear skies & Good seeing
Edit typos

Edited by PKDfan, 16 September 2021 - 09:39 PM.

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#58 Leaf

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Posted 16 September 2021 - 10:52 PM

Hi Leaf! Having used a C8 with reducer at Grouse mountain in Vancouver, a 12mm 82° or greater apparent field eyepiece should make all of the Messier list objects sparkle, a ~2mm exit pupil and ~100×.

It will be a most used eyepiece.

Thats my best recommendation for a most useful eyepiece for a reflector user of your size and focal length.

Saanich or the area near has the 72" Dominion Astrophysical Observatory so seeing will be excellent more often than not, I would think.
Are you close to that?

I hardly ever saw the stars twinkle much, when I worked there for a few months during summer, when I was much younger.

Go slow and train your brain to exert every last scrap of information when observing the planets so that when they become more favourably placed you will be rewarded with great joy and happiness as you unlock previously hidden details.

For me, every time out when I first got the C8 was a greater and greater need to see as much as possible so I learned to slow down and OBSERVE every object I found.

More and more information was transfered/assimilated, its as if I added aperture to the scope.

Now with that experience under my belt, using my 4" apo is very rewarding as I believe I am utilizing every last millimeter of aperture I have.

Last thought, parroting others, buy once cry once.
Quality costs!


Clear skies & Good seeing
Edit typos

Thank you for the recommendation, I will keep it in mind waytogo.gif The DAO is in the region yes, however I live near Langford so it's a bit of a drive for me. I think they're closed for now as well. There's a few different hills and small mountains I could potentially go to. I like the convenience of stargazing from my yard though.

 

Going slow and enjoying the view is the way to go for sure. I view maybe three or four objects a night currently so that gives me plenty of time to appreciate them. The moon, Jupiter, Saturn, and I caught the last glimpse of Venus before it dipped below the horizon the other day. Would like to see Neptune but I think my view of it in the early night is blocked by trees. Unfortunately I can't afford to stay up past midnight most nights, at the latest. Usually not even that.

 

Ugly skies and bad seeing tonight I'm afraid!


Edited by Leaf, 16 September 2021 - 10:53 PM.

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#59 Don H

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Posted 18 September 2021 - 05:08 PM

Thank you for the information, I will look for these DSOs next time I get a clear night waytogo.gif How helpful are filters in bringing these things out? Will they be a worthwhile investment for me in the future?

...

You might want to let the moon depart by waiting until later next week. DSOs will appear much better in a moonless sky. The main benefit of a filter will be on nebulae. I would say one may be a worthwhile investment in the future. However, with your current aversion to changing eps, I would get used to handling a couple of those at each viewing session. Once you feel your skill and confidence have increased, then you could add the bit trickier procedure of screwing your filter on and off. Sometimes I like to put a filter on an ep while indoors, and then keep it on outside to simplify viewing.




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