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Focusing?


TonyMan
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I'm kinda new to this and managed to get good photos of the sun & the moon, but they are fairly large objects and easy to focus. I tried for Jupiter and Saturn the other night, but the photos in the videos, and the videos themselves, looked fuzzy. I've mainly been at 400 ISO and have used 1/30, 1/45, 1/60,  and 1/90 of a second. When I run the videos, or look at the individual frames I can almost see the bands on Jupiter, but it's fuzzy. I haven't run these through any stacking software yet because that is also new to me, and wondering if that would clear anything up.

When I have Backyard EOS running on my laptop I just never seem to get a good focus on the screen. Should I really be able to see those planets clearly , or am I asking for too much. My focuser is a two speed one so am trying my hardest to slowly find a good focusing point. I just never see anything that looks in focus.

I've included a couple of examples. I am using:

Celestron Evolution 8"

6.3 focal reducer on some

Canon Rebel EOS T6

 

Thanks

Planetary_Tv160s_400iso_1056x704_20200807-23h47m22s_000005.jpg

Planetary_Tv190s_400iso_1056x704_20200807-23h15m41s_000001.jpg

Planetary_Tv145s_400iso_1056x704_20200807-23h46m52s_000003.jpg

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Tony,

All Celestial objects that you look at through the telescope are essentially an infinite distance away. I would suggest that you focus on a bright star. This uses LiveView on the Frame and Focus screen. The BYE User Guide explains how to use the Focus Metrics to achieve critical focus on a bright star.

Once you are focused, you can move to the planetary object. The live Planetary image should be dark, with Jupiter's equatorial bands just becoming visible. You will be able to brighten the image during processing.

I hope this helps.

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Thanks for the info. My biggest problem is that from my driveway there is a spot where I can see the planets for about 2-3 hours. Very hard to see a bright star there. I'll have to look around for a better place to try from. I'll read the other link mentioned too.

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Thanks. 

Since I am using prime focus, I’m not sure how I could get a Barlow into that configuration. I have a 2” And 1 1/4 “ Barlow, but would have to go to eyepiece projection then, but don’t have a way of connecting the Camera to the Barlow. I do have a T ring adapter and T adapter that would allow me to attach my Baader eyepieces to the camera. Are you suggesting I do that and put the eyepiece into the Barlow? I’ve looked around but don’t see what I could get to just connect the camera directly to either Barlow.

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10 hours ago, TonyMan said:

Since I am using prime focus, I’m not sure how I could get a Barlow into that configuration. I have a 2” And 1 1/4 “ Barlow, but would have to go to eyepiece projection then, but don’t have a way of connecting the Camera to the Barlow. I do have a T ring adapter and T adapter that would allow me to attach my Baader eyepieces to the camera. Are you suggesting I do that and put the eyepiece into the Barlow? I’ve looked around but don’t see what I could get to just connect the camera directly to either Barlow.

F/10 (2000mm) Prime Focus is better than f/6.3 (1260mm) "Reduced", but for the C8 you can still usually support about 3500-4000mm Focal Length (2x Barlow) under "Decent" Seeing Conditions with a DSLR.

No, I am not suggesting Eyepiece Projection - although that too is another way to increase the Effective Focal Length of the Scope.

It's a bit confusing regarding references to "eyepiece into the Barlow", as a Barlow is piece of inline Optics which extends the Focal Length.  I'm unaware of any Barlow design which Requires (or even allows) an Eyepiece to be fitted within it - most will have either Threaded or Compression Ring (or both) connection for the Camera T-Adapter.

Perhaps you can provide Model Number or Link to your Barlows...

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I appreciate your comments, but am a little confused by some of the, so let me explain. First of all my Barlows are a 2" GSO 2x and a 1 1/4 Celestron Omni 2X. I typically use 2" eyepieces, but that is kinda irrelevant here. Your response to "eyepiece into the Barlow" kinda looses me. Both Barlows I own are put into the focuser or diagonal and then an eyepiece is inserted. I was under the impression that was how all Barlows worked but maybe my choice of words was wrong. Anyway, on to what I have and how I see I can use it.

I have the Celestron T-Adapter-SC, #93633-A. That connects to the camera and the visual back on the Evolution. Since this screws on to the visual back I do not see how a Barlow can be inserted, unless there is some other adapter I would need to do prime focus. However, just now I unscrewed the two halves of the 2" Barlow and found the part with the lens can be screwed on to the T adapter. with this arrangement I could try eyepiece projection by inserting it into the diagonal. If there were something that would allow me to connect the end of the Barlow to the visual back that would work, but I'm not sure what that would be, but I can look around. However, weather predictions don't show a good night for over a week unless things change. 

The other way of doing eyepiece projection I was referring to goes like this. I have two Baader Hyperion eyepieces and a Baader 8 - 24 Mark IV Zoom eyepiece. I also have a Baader T Ring adapter and T adapter that would allow me to screw any of those eyepieces to the camera. (The zoom eyepiece does take a little work to remove movable focusing ring to get to the threads.) I could attach one of these to the camera, and the Barlow if needed, and put that into the diagonal. It's a little bit heavy doing that, but it can be done. I tried with just a 13mm eyepiece the other night, but forgot to mark which images were done that way. I'm just not sure if its worth all that trouble.

To me, it seems the easiest configuration would be if I could find something that would clamp down the smooth end of the Barlow and have a connector to thread to the visual back. Like I said, I'll have to look around for that kind of item. In the meantime if I haven't explained this clearly, or have stated something wrong, let me know - I have no fear of helpful criticism. AS I stated above, I have at least a week of cloudy skies before I can go out again, so hopefully enough time for me to get it straihjt.

Thanks

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I have been looking for the part that you need for over an hour and cannot find the one that I have. Neither can I find that part on any web site. I posed the question, vie email to a vendor. I will let you know what I hear.

Basically what you need is an EdgeHD 2" Adapter. It is often used to allow a non-Celestron diagonal with a 2" barrel to be connected to the rear cell of an EdgeHD SCT. Note that this part is specific to the EdgeHD so a standard SCT 2" adapter will not work. Then you can put Barlow into the 2" adapter and your camera into Barlow. Of course you would need a T-Ring, a T-adapter, and a 2" T2 adapter in between the Barlow and the camera.

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What about this: https://agenaastro.com/celestron-sct-to-2-visual-back-adapter-93661.html

Looks like it would screw onto the visual back and then allow 2” eyepieces or Barlow to be connected. I’d only worry about the weight of the camera. If you search for visual backs on their page it seems there are other ones that cost more, possibly more secure. 

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The typical order of parts is:

  1. C8 -> [Visual Back or Celestron 6.3 Reducer] -> optional Extender -> Diagonal -> Eyepiece
  2. C8 -> [Visual Back or Celestron 6.3 Reducer] -> optional Extender -> T-Adapter -> T-Ring -> DSLR
  3. C8 -> Visual Back -> Barlow -> optional Extender -> Diagonal -> Eyepiece
  4. C8 -> Visual Back -> Barlow -> optional Extender -> optional T-Adapter -> T-Ring - DSLR  (use T-Adapter if Compression Ring end on Barlow / else use T-Ring if Threaded end on Barlow)

There are unfortunately enough variations in equipment (Barlows, Extenders, T-Adapters) that you will need to work from these generalizations to the specific combo for your own gear.

(Note:  I added to the confusion because of your phrasing "Are you suggesting I do that and put the eyepiece into the Barlow?", although it is clearer now that this is not actually what you meant to describe.  We're good...)

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Actually, this is what I decided on. Based on comments on this one and the other one, I like the idea of 2 thumbscrews to keep things straight and handle the weight.

https://agenaastro.com/blue-fireball-2-sct-visual-back-sct-2-adapter.html

So I will wind up using s3igell's 4th suggestion, C8 -> Visual Back -> Barlow -> optional Extender -> optional T-Adapter -> T-Ring - DSLR  (use T-Adapter if Compression Ring end on Barlow / else use T-Ring if Threaded end on Barlow), but without the optional extender. The only issue I have to correct is where the Barlow screws into the T-Ring adapter. It seems the Barlow doesn't have long enough threads for the T-Ring flush surface to touch it so there is a tiny bit of play. I think my choices are to fashion some kind of washer to fill the gap temporarily, and permanently to see if I could find a machine shop that could cut a couple more threads into the Barlow.

After all this I can't believe has simple the solution is. I guess it took just letting others give me some advice so I could search the right places.

Hats off toastroman133 and s3igell, you folks were great!

 

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That Blue Fireball adapter is a good choice.  I actually have one for my C9.25 (packed away in Colorado).  If I remember, it grips the Nosepiece of whatever is inserted quite tightly.

As for your Barlow-to-T-Ring Connection being "loose" - are you sure it is not the T-Ring Bayonet Connector being a bit Loose in the Camera Body??  That is a common issue with many brands of T-Ring (with little one can do to address it).  But, if it is the T-Ring Threads that are a bit loose, then a washer (even if made out of gasket material) should work.

 

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astroman133 - My scope is not an Edge HD, it's an Evolution 8". The threading on the piece is T24, so it should be OK. Plus looking through reviews I see folks have used it on C8, 8SE, and other Celestron SCTs, so I feel good about it.

S3igell -No it's not loose in the camera body. Picture this: camera - T Ring adapter - Barlow. When I screw the T-Ring adapter to the Barlow that joint has a slight bit of play in it. I can see that the Barlow threads are 1, possibly two threads shorter than the threads on the T-Ring adapter. For right now I agree a washer would help, but I sure would like to find a machine shop that could cut me a couple more threads,

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You will probably also want to research your Barlow for its "Recommended Back Focus".

From your description, you are using the threaded connection as for a Backfocus of 55mm.

Many Barlows are 55mm, but some are designed for 75mm or 105mm (either of which would mean you would need to add an Extension Tube between Barlow and T-Ring - and might forego the need for machining additional threads).  Its worth confirming the specs on your Barlow.

 

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Easiest way is to check the vendors who are selling the same Barlow.  They will usually list the Backfocus as part of the Specs.

If all else fails, take a couple of Pictures through it on your C8 (mounted or set on some solid surface pointed at a distant (1-2 miles) target - using the best Focus you can attain.  If the images are good edge-to-edge, you have the correct Backfocus.  If the corners are really bad, you don't...

 

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