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Need some general advice on an APM 152/1200

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#1 jriastro

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Posted 14 July 2013 - 12:42 PM

Hello everyone,

I had a couple of questions I was hoping I could get some help with. I'm setting up an APM 152/1200 CNC II. I'd like to look visually through it to see how good the optics are during the day before hooking up the camera at night.

1. Should I use a diagonal? Will it be better quality if I just put the eyepiece in with no diagonal?

2. I was going to use a 25mm eyepiece which gives 48X for the 1200. Is this too much magnification for daytime observing? Will I be able to focus on something a 1/4 mile away? I just want to see visually how the optics look.

3. Any suggestions on magnification I should use during the day to focus on something a 1/4 or so mile away? Eyepiece size?

Thanks in advance for the help.

#2 Eddgie

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Posted 14 July 2013 - 01:33 PM

If it is a high quality diagonal then it will not degrade the image in any way, but as long as you can reach focus either way, it doesn't really matter whether you use a diagonal or not.

You really can't tell much by looking during the day unless you have a known good telescope to compare it to. I am sure the image will be fine.

If you use a target too far away, seeing can make it difficult to get a sharp, stable image, so to me, closer is better, but again, unless you have something to compare it to, you really aren't doing much of a test. The scope could have 1/4 wave of spherical abberation and this would not be easy to see during the day without using very specialzed test targets.

A nigtht time star test is a much more sensitive test than daytime testing. Even some poor telescopes can provide what appears to be a sharp image during the day and not be great optically.

If it is an APO though, I would recommend that you use high power to focus on the edge of a leaf against the sky to check for fringing.

Again, this test is even not that useful unless you have a basis for comparison, but if it is an APO, you shoud be able to look at the very edges of distant objects and not see much color fringing. Ah, but there we go... If you see some, is it within the design limit of the manufacturer? Ha ha... They won't say becaues they don't test on tree leaves.

Not trying to discurage you from looking at the scope before buying, but there is little from an optical quality stanpoint that can be easily discerned during the day without using high quality test charts or another sample to compare against.

#3 jriastro

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Posted 14 July 2013 - 01:38 PM

Thanks for the info. I actually own the scope already. Just wanted to see what it looks like during the daytime. The rest of its life will be for imaging.

I actually just tried it and am having a hard time getting it into focus. I have the focus all the way out to get a clear image of some trees 50 or so yards away. This is with the 25mm eyepiece.

#4 ggalilei

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Posted 14 July 2013 - 02:09 PM

You may need to look farther away than 50 yards.

#5 jriastro

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Posted 14 July 2013 - 02:25 PM

Ok, I got it to focus. I had to add two extension tubes. one 80mm and one 60mm. In addition I had to adjust the feather touch focuser out about 90mm. Almost to the max of 110mm. I was able to get crystal clear focus this way.

Does this seem right? It seems like I had to add a lot of extension to get it to focus. I took some pictures that are below. Does this seem like too much extension to be able to get the 152/1200 in focus? Again, I was only looking at trees maybe 70 yards away.

This is the whole setup.
Posted Image

Zoomed in focuser, extension tubes I had to use to get it to focus. Does this seem excessive for 75 yards away or ok?
Posted Image




#6 johnnyha

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Posted 14 July 2013 - 02:36 PM

That seems about right. The tube is probably "bino-friendly" so a few inches shorter, which usually requires an extension for mono viewing - although maybe not with the extra long 4.5" drawtube of the magnificent FT3545. But then also when you remove the diagonal you have to add an extension to make up for the length of the diagonal. Also it requires more length to look at stuff that's closer to you, this scope is made primarily for infinity viewing. Congrats that's a terrific setup, and good luck!

#7 jriastro

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Posted 14 July 2013 - 02:51 PM

Thanks. Ok, I put the diagonal in and was able to remove one of the extension tubes and the focuser only needed to come out 45mm or so. Feel much better now! I didn't realize how much the diagonal adds to length. It was a dramatic change.

I still need to mount the SV80S on top as a guide scope. I'm sure I'll do some imaging with the SV80S too once I figure it all out. The SBIG 11000 camera is what makes me a little nervous. It gets heavy on that end with the filter wheel attached.

Thanks for the input everyone.

#8 Hermie

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Posted 14 July 2013 - 05:55 PM

As you've discovered, you just need an extension to view without a diagonal.

As far as magnification, feel free to push it. During the day there is often a lot of turbulence in the air from solar heating, but if its smooth you can use all the magnification you'd use at night. It gives you an appreciation of what we are doing with those photons when you actually see what 300x is in an everyday scene.

Hermie






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