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Midnight Dan
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Reged: 01/23/08

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Re: NexStar 5SE & 6SE queries new [Re: Lobot]
      #5536983 - 11/24/12 10:31 AM

Hi Robin:

The problem with rechargeables is that they are usually Nickel Metal Hydride or NiMH. This means that each cell is 1.2v instead of the normal 1.5v of a non-rechargeable alkaline battery. When you string 8 of them together, you only get 10 volts instead of the needed 12 volts. They will work for a little while, but they quickly drop below the voltage needed to power the mount.

A power tank is a popular choice because they are available everywhere, are reasonably priced, and usually have the needed cigarette lighter jack built in. But they are heavy, and you have the issue of the cord wrapping around the base during use.

Another option is to get a 10-cell NiMH battery pack that rides on the base of the mount. With 10 cells instead of 8, you do get the 12v that the mount wants and they work quite well. They're much lighter than a power tank and you eliminate the cord wrap issue because the battery pack moves with the mount. The only downside is you have to wire up a connector yourself. Here's my setup:



I got the battery and charger at:
http://www.onlybatterypacks.com/showitem.asp?ItemID=11075.37

Mine lasts 4-5 hours powering the scope and 2 dew heater straps.

Quote:

ii) What sort of magnification will this be approximately? I initially thought that the adapter would use the eyepiece somehow, but it does seem to fit within it!!




There's three kinds of AP (astrophotography): afocal, eyepiece projection (EPP), and prime focus. Afocal is where you just hold your camera up to an eyepiece and snap away. In this case both the camera's lens and the eyepiece are in place and both affect the magnification. However, since these optical systems were not designed to work together, the results are pot luck.

In EPP, you remove the camera's lens but you leave the eyepiece in place. In this case, the EP projects the image directly onto the camera's sensor. The EP does contribute to magnification and changing EPs will change the image size. This setup requires some way to mount the camera to the EP. There are some EP's like the Baader Hyperions that are designed specifically for this purpose. They have a thread around the eye lens so you can screw on an adapter that mates to a T-thread which then connect to your camera. EPP is much better than Afocal but still, the EPs are designed to work with your eye, not with a flat sensor. They often curve the field somewhat and usually do not provide as good a result as with prime focus.

Prime focus is using the scope without an eyepiece or a camera lens, to project the image directly onto the sensor. This provides the best quality image, but of course it limits you to one image size. You can use barlows and focal reducers to change the image size, and they will do a better job than an eyepiece because they are simpler designs and tend to leave the image cleaner and the focal plane flatter.

Focal reducers can be pretty easy to use because they screw right onto the back of and SCT. You then jus use an SCT-to-Tthread adapter on the back of the focal reducer and a T-ring on your camera, and you're good to go.

Barlows are a little trickier because you don't find them with an SCT thread. To allow the use of a barlow, you have to get to a 2" eyepiece sized tube so you can use a standard 2" barlow in it. So the chain of adapters you need is:
SCT > 2" visual back > 2" Barlow > 2" nosepiece-to-Tthread adapter > T-ring > camera

-Dan


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hopskipson
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Reged: 06/24/10

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Re: NexStar 5SE & 6SE queries new [Re: Midnight Dan]
      #5537394 - 11/24/12 03:32 PM

"Barlows are a little trickier because you don't find them with an SCT thread. To allow the use of a barlow, you have to get to a 2" eyepiece sized tube so you can use a standard 2" barlow in it. So the chain of adapters you need is:
SCT > 2" visual back > 2" Barlow > 2" nosepiece-to-Tthread adapter > T-ring > camera"

I use a Tele Vue Powermate that has an adapter that threads to the lens part of the barlow and has a T-thread for the camera. Works great in the 2" diagonal.

James


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Midnight Dan
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Reged: 01/23/08

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Re: NexStar 5SE & 6SE queries new [Re: hopskipson]
      #5537697 - 11/24/12 07:02 PM

Hi James:

Yep. Although, having a 2" diagonal is like having a 2" visual back. Both serve the purpose of converting the SCT thread to a 2" barrel receptacle. I like to avoid using a diagonal for AP because it seems to attract more dirt and dust particles than other other piece of optics I own. Never could understand why, but when I clean my optics, it's always quite dirty. Plus, attaching directly to the back of the SCT eliminates the mirror as a potential source of misalignment.

Since your Powermate has a T-thread on top, it sounds like it eliminates the need for the 2" nosepiece-to-Thread adapter. That's handy!

-Dan


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Lobot
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Reged: 10/09/12

Re: NexStar 5SE & 6SE queries new [Re: Lobot]
      #5540324 - 11/26/12 01:38 PM Attachment (17 downloads)

Hi everyone, thanks again for all of the suggestions. I had another 10 minute window in the cloud tonight & was able to take a half-decent photo of the moon....it's a bit over-exposed, but before I could take another the cloud descended!

Link below to my flickr account, if the attachment didn't work:

http://www.flickr.com/photos/69979581@N03/8220680097/in/photostream

This is fun

Cheers

Robin :-)


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Arthur Dent
Galactic Hitch-Hiker
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Reged: 10/23/08

Loc: South Yorkshire, UK
Re: NexStar 5SE & 6SE queries new [Re: Lobot]
      #5540675 - 11/26/12 05:09 PM

That's a lovely shot Lobot - that image is lovely and crisp and has a real 3D fell.

Prime focus or afocal? Single frame, stacked or mosaic?

Any details would be welcome.

Art


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Peter9
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Reged: 10/30/08

Loc: Yorkshire - Born & Bred
Re: NexStar 5SE & 6SE queries new [Re: Arthur Dent]
      #5541514 - 11/27/12 04:27 AM

Nice shot of the Moon Lobot given you only had a 10minute window.

Thanks for posting.

Regards. Peter.


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Lobot
member


Reged: 10/09/12

Re: NexStar 5SE & 6SE queries [Re: Peter9]
      #5542093 - 11/27/12 01:05 PM

Hi, thanks for the comments, really appreciated! Details as follows:

Taken using a Canon EOS 550d, attached to the Star Diagonal via a Celestron t-adapter (plus t-ring!): http://www.amazon.co.uk/Celestron-T-Adapter-Universal-1-1-4/dp/B0000665V6/ref...

Single exposure: ISO 400, 1/250 sec. This was the best of 5-6 photos; I'm still getting used to the correct settings, but am determined to do far better...I've only used a 70-300mm lens before so this is all new to me!!

Cheers, Robin


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