Focus 'Bottoms Out' Using Different Eye Pieces

[TimeScorpion7]

Hello,

I just started using my NextStar 6SE for the first time. I got everything set up and aligned pretty well but am having trouble focussing. I started with the moon because I figured it would be easiest. I started with the 25mm eye piece and it focussed pretty well but I could only see the edge of the moon. I want to see the entire or just a bigger part of the moon. I tried moving up to the 32mm, then the 40mm and even back down to a 10mm. On all of those lenses I couldn't seem to get them in focus. I could see them getting sharper and sharper but then I hit the end of my focussing adjustment and couldn't go any further.

Do you guys have any recommendations so that I can focus using the other lenses and see either a bigger part of the moon or in more detail?

[johninderby]

First thought. Are you using the supplied diagonal as putting the eyepiece directly into the scope withoit it won’t allow you to focus properly. as you won’t have enough focuser travel.

Edited May 2, 2020 by johninderby

[TimeScorpion7]

Yes, I'm using the supplied diagonal.

[johninderby]

The 6SE has more focuser travel than you would need with any normal eyepiece on any target in the sky so not sure what the problem is if the focuser is working properly.

Perhaps a good idea to turn the focuser knod as far as it will go in one direction and then back the other way a couple of times to make sure the focuser is working properly and distribute the grease in the focuser evenly. 

A photo of the scope so we can see the setup would help.

Edited May 2, 2020 by johninderby

[Ricochet]

51 minutes ago, TimeScorpion7 said:

it focussed pretty well but I could only see the edge of the moon.

This suggests to me that you are not actually pointing your telescope at the moon. Instead, you are pointing your telescope near the moon and seeing some sort of internal reflection off the insides of your telescope. When you point your telescope at the moon you will see exactly the same phase as you see when looking up at in the sky. 

To correct this, the first thing that you should do is to try to align your finderscope in the daytime. Put your telescope somewhere where you can see far into the distance and centre the telescope on the furthest object that you can see and easily identify when you're not looking through the telescope. Use your highest focal length eyepiece for this. Next, adjust the adjustment knobs on the finderscope/rdf so that it is also pointing at that same object you can see through the eyepiece. Your telescope should now be reasonably well aligned, but you may still need to manually scan around a bit to find the moon the next time you use the telescope at night. Once you have properly found the moon, you can use it to dial in your finderscope.

With regards to magnification, you find it by dividing the focal length of your telescope by the focal length of the eyepiece. This means that your eyepiece with the highest focal length printed on it has the lowest magnification, and the one with the shortest focal length has the highest magnification. When attempting to find things I would always start with the lowest magnification. However, if your 32 and 40mm eyepieces are Plossls, they will actually show the same amount of sky so it will not matter which of these you use as a finder.

[Peter Drew]

There should be plenty of focus travel with or without a diagonal and any eyepiece.  You should be able to see the whole of the Moon image with a 32mm or 40mm eyepiece.  The point of focus is quite precise, it's quite easy to overshoot, try doing it slowly.    🙂

[Louis D]

You should have a 0.83 degree true field of view with supplied 25mm Plossl.

   50 degrees AFOV/(1500mm telescope FL/25mm eyepiece FL) = 0.83 degree

Thus, the moon at 0.5 degree should easily fit in the eyepiece field of view.

[TimeScorpion7]

Okay! Thank you for all this advice. I'm going to adjust the finderscope today and then try again tonight. I'm assuming that's what made my Star Allign off and made it so I was only seeing an inner reflection of the moon? Do you guys know if its possible to manually adjust the positioning using the motor after its been aligned? The movement arrows don't work and I feel like I'm missing something. 

[DaveL59]

are you certain the movement arrows aren't working?

Try it and listen close to the mount and see if there's any motor noise as once the goto has fast slewed to target it'll switch the slew speed to min for tracking and the movement is barely noticable and will take ages to adjust position at that setting. You can increase the slew speed once it had moved the scope to shift to a faster gear as it were, just select via the handset and then fine tune the aim before confirming. Use a low-ish speed setting tho, say 2 or 3 not the faster ones or you'll be wildly swinging the scope away from target. Have a practise in daylight to figure these bits out before going out to play in the dark. It helps a lot. You don't need to see any stars, just let it pick a target and try adjusting etc..

[RT65CB-SWL]

Hi @TimeScorpion7 and welcome to SGL. 

Are your eyepieces of the same brand?

Some brands are 'parfocal' meaning you should not need additional twist on the focusser to bring in to sharp focus.
Don't assume that you have sharp focus with one eyepiece, the others are going to be in focus as well.

I have a modest collection and I make a few minor +/- twists of the focusser to bring the object in to sharp focus with
each, even it is of the same brand. 

[TimeScorpion7]

I used it last night and it worked great! Was able to see the Moon, Saturn, Mars, and Jupiter. I figured out the manual adjustment after alignment and also fixed the focussing issue which all helped a lot. Moving forward, whats the best way to see more detailed pictures of the planets and also seeing deep space objects? Would it be to get an eyepiece with higher focal length? I haven't used the Barlow lens yet... would that help? I guess the constraints would be the diameter of the telescope itself and the all of the Los Angeles light pollution.

I must say it is a privilege to get this perspective on our existence. It really put me in my place.