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#1 mike eddleman

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Posted 18 August 2019 - 04:59 AM

I tried searching for the answers but didn't find anything or plain just not understanding what i'm reading I guess, but Of course I'm new to all of this, I bought a used 10 inch dobsonian and extra eye pieces, they are 6,8,28,32 and some others and a 2x doubler, the telescope is a 1200mm at f 4.7 friday night was a full moon and I really thought with all that i bought I would have been really able to see just about inside the creators but I did see the some outlines of them but not really as close as I thought, I'm going by by looking at youtube videos of others with the same equipment as mine, just wondering if i.m doing something wrong or am i expecting to much from what i bought? any thoughts?



#2 ngc7319_20

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Posted 18 August 2019 - 05:32 AM

Full moon is not the best time to see details on craters.  The lighting is very flat, and contrast is poor.  Better time will be in a few days, like last quarter.

 

What eyepiece were you using?  Sometimes too much power (especially if the air is unsteady) will make disappointing, blurry views.  A great deal depends on whether the atmosphere is steady.  Rapid temperature changes and wind tend to make for blurry views.


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#3 mike eddleman

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Posted 18 August 2019 - 05:39 AM

I tried every eyepiece i had just to see what each would do, like I said I'm new so wasn't really sure what to expect so I tried them all, I also have a moon filter that I was using. 



#4 ngc7319_20

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Posted 18 August 2019 - 05:49 AM

If the low magnification eyepieces like the 28mm and 32mm gave uninspiring views, it might be just the low contrast at full moon.

 

I suppose the scope could also be out of collimation.  Maybe the mirrors need to be adjusted.  Have you done anything about aligning the mirrors since you got the scope?  Often people will use a laser collimator for this.  Was there a manual with the scope, and did it explain how to check the collimation?


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#5 GunArm

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Posted 18 August 2019 - 06:03 AM

Was it an issue with the detail you could resolve, or was it less magnification than you hoped for?  My father got an 8" dob and was expecting more zoom on the moon. 

 

Thing is with a big wide dobson like that what you are paying for is aperture, how much light it lets in for seeing more dim objects (not such an issue for the blinding moon).  A 1200mm scope is not wide field but not super long like a planet viewing SCT either, and that doesn't make it bad.  When I first got into this my assumption was that telescopes are all about zooming in, a good scope is one that zooms more etc.  Really, magnification is just one of a few opposing things which people of different interests can choose to optimize for.  There are plenty of sights and less headaches with more moderate magnification.  More zoom means more moving the telescope.  More zoom means less brightness, for a given aperture, and usually brightness is king for visual viewing.  A 10" dob is optimized for the most affordable way to capture a ton of light for visual viewing of dimmer objects.

 

Although we can't see what you saw, you can check out this page https://astronomy.to.../field_of_view/ to simulate what you would expect to see with a given setup.

 

Since the scope has a fixed focal length, there really isn't any way to misuse it that would reduce it's zoom, the magnification is only affected by eyepieces.  I'm pretty sure that anything you were doing wrong like having it out of collimation or issues with the optics would either make it dim or blurry, but not affect magnification.

 

If I were you, I'd go out on the new moon at the end of the month and see if you can find a globular cluster with that scope.


Edited by GunArm, 18 August 2019 - 06:08 AM.


#6 Ulmer Spatz

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Posted 18 August 2019 - 06:11 AM

Full moon is not the best time to see details on craters.  The lighting is very flat, and contrast is poor.  Better time will be in a few days, like last quarter.

This ^. Look at close-up photographs of craters. When the light comes from the side (like it does when the moon is not full), it throws strong shadows. In a few days when the moon is no longer full, your views will most likely match those photographs.

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Edited by Ulmer Spatz, 18 August 2019 - 10:25 AM.

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#7 williew

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Posted 18 August 2019 - 06:37 AM

     The full Moon might lack features, but the edges of the Moon should be crisp. Have a look around during the day to see how distant objects focus. Use your 28 or 32mm EP. Also, you can check out Jupiter and Saturn.



#8 sg6

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Posted 18 August 2019 - 07:12 AM

Half the question is what did you expect to see.

Full moon is impressive if you get the whole lot in view with a bit of the universe framing it, so looking at a 1 degree view and that is around a 20mm eyepiece. 1 degree in EP is around 60x and 60x is a 20mm eyepiece. The 28mm should be good.

 

After that I would say the direct lighting of a full moon lessens the impact when viewing a portion of the moon. I tend to stick to full views or the edge. I have no idea which crater is which. Been to a few where a crater was centered and talked about, and to be honest could have been any old crater. Suspect at times it was - I know some of the people doing the talking.

 

Thinking back to the crater viewing the magnification would have been up around 200x, think it was always said as 183x or close. You are in that area with the 6mm and 8mm.

 

If a crater can be isolated at that then you should manage the same. So that leaves the illumination.

 

Try the edge, should see the crater edges and mountains in silhouette, may even see a star transit in the dips between peaks.



#9 mike eddleman

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Posted 18 August 2019 - 07:12 AM

I used the collamation eyepiece with the little hole and the dot is a little off center, the guy i bought it from said it was close enough, ill look at it again, but i really think it was due to the full moon, after reading the answers I gave gotten, I could see the edge of the moon good and crisp, i'll keep experimenting with it, and I am going to read up on the eye pieces more, and thanks to all for the great help with getting it going in the right direction


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#10 cookjaiii

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Posted 18 August 2019 - 07:26 AM

A f/4.7 telescope is very sensitive to mis-collimation. Spend some time to learn this skill, and collimate at the start of every session.  It is worth the effort.  

 

Make sure to give the telescope mirror plenty of time to reach thermal equilibrium.  A fan will help with this. This can take more than an hour depending on the temperature difference.

 

Avoid observing with your line of sight over house roofs, asphalt parking lots, bodies of water.  All these can contribute to thermal air turbulence.

 

Congrats on the new scope.  A 10" is a lifetime scope and it's an awesome way to start in this wonderful hobby.


Edited by cookjaiii, 18 August 2019 - 07:26 AM.

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#11 Mike W.

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Posted 18 August 2019 - 07:28 AM

Morning, things you can do also for lunar viewing is filters, not color filters but neutral density and polarize filters.

 

Sometimes too much light will wash out detail, yes waiting for a few days for the shadows to help.

 

I'd suggest two neutral density filters , a 13% and 25% then stack either of them with a polarize filter for better contrast.


Edited by Mike W., 18 August 2019 - 07:29 AM.


#12 clusterbuster

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Posted 19 August 2019 - 01:50 AM

i suggest that you check out collimation by STAR TESTING. Check out some of the you tube videos. COLLIMATION is the key.

 Mark


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#13 ww321q

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Posted 19 August 2019 - 01:30 PM

I used the collamation eyepiece with the little hole and the dot is a little off center, the guy i bought it from said it was close enough, ill look at it again, but i really think it was due to the full moon, after reading the answers I gave gotten, I could see the edge of the moon good and crisp, i'll keep experimenting with it, and I am going to read up on the eye pieces more, and thanks to all for the great help with getting it going in the right direction

Start with a sheet of paper opposite your focuser and look through your collamation eyepiece. That will help show if your secondary mirror is lined up with the focuser. Make adjustments as needed. Take out the paper and the collamation eyepiece and look through the focuser again with the focuser all the way in . You should be able to the edge of your primary mirror all the way around if you move your eye around. Also note the reflection of the secondary mirror in the primary mirror along with center dot in the mirror and if you back your eye up just a little , you'll see it too. Now put the collimation eyepiece back in and see if the center dot and secondary reflection are concentric and centered in the view. Making adjustments may be more than fooling around with the secondary adjustments. Anyway thats how I do it and then use a laser collimater to finish. I enjoy looking at the moon at high magnification too. I rarely even look at it when its full because everything is washed out and no shadows to show contrast.  




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