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Old Sunday 30th May 2010, 01:38   #1
DRodrigues
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Siebert Optics Power Mag Wheel 1.0x to 3.0x

If you want zooming your telescope without changing barlows this might interest you.
I intended to test it for photography last winter but had problems with my astrotelescope so I asked a photo friend to test it for me. Examples of the results are available at
http://celestron80ed.blogspot.com/20...rans-test.html - Pedro called it ATIK since is the brand of the filter wheel that Siebert used for this version of PMW.
At higher magnification his working with 600*1.4*3=2520mm plus 1.6x crop factor - all photos were taken at the end of the day so that's the reason for the colours shown. I asked him a photo of a bird closer, also at maximum magnification. I cropped it, tried to fix colours (without great success...), resized it and enclosed. Also included a photo of the combo - the wheel can be also used if a lower position.
Pedro enjoys this barlow wheel. It's not a cheap piece but is practical and of good quality. Hope to test it my self latter...
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Old Saturday 5th June 2010, 13:13   #2
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I used to have a Siebert Wheel with 1x, 2x, 3x mags hooked up to a pair of binoviewers and my 300mm dobsonian telescope. Made for awesome all-in-one astronomy viewing with a pair of good widefield eyepieces. Anyway, I agree that Siebert builds products of very high quality, and that Mag Wheel is like nothing else on the market. Best thing is that you can talk to Harry Siebert directly over the phone to have one of many different magnification setups custom fit for your needs. Good luck with the test, I look forward to reading of your own findings.
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Old Thursday 21st April 2011, 15:28   #3
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I enclose an example of the PMW 0-3X magnification changes with the Moon (near full Moon, in one of the days where the Moon was closest to the Earth), Just resized to 1200, 90% quality, with the TMB92+BS1.6x+NEX5.
Putting spacers within the PMW and the camera increases the magnification differences. The positions/magnifications are:
1-0, 2-1.6x, 3-2x, 4-2.5x, 5-3x
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Old Thursday 21st April 2011, 15:40   #4
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Another example of the PMW 0-3X magnification changes with a Female teal (resized to 1200 and 85% quality), with the TMB92+BS1.6x+NEX5.
Putting spacers within the PMW and the camera increases the magnification differences. The positions/magnifications are:
1-0, 2-1.6x, 3-2x, 4-2.5x, 5-3x

I like this piece since allow me to zoom without changing barlows. It's also great to do HD films.
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Old Saturday 23rd April 2011, 04:05   #5
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Bravo David. So you can basically change the magnification at the fraction of a second. Two things (slightly off topic), the 0X pic does look less sharp when compared to the others, in both the duck shot and moon shot. Are they just a co-incidence with the focusing or just my eyes or monitor setting. The other question. The magnification of the last pic in comparison are more like 2 x or less instead of 3 X. Are the photos cropped? Bonus question: LOL. Will the variation in magnification affect the infinity and minimum focus distance of the setup?
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Old Thursday 28th April 2011, 23:32   #6
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Hi David! nice review. Where you bought it? I see that you are from Coimbra, and Im from Vigo. Im thinking on visit the Lagoas de Bertiandos.

Nice to meet you!
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Old Friday 29th April 2011, 00:02   #7
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Alphan,
The 0x appearing less focused is probably a coincidence as also because is more difficult to focus smaller images... I enclose another series of photos - Anas querquedula - not so usual here and these ones were at a big distance.
You are right about the zooming factor - I already noticed that it increased less then I expected at 3x since at the day I took photos to the Moon I did the same with my Optolyth 100 with the Nikon FSA-L2 and this last one had higher magnifications. Comparing the sizes of the Moon I reached the following FL:
1 945mm 1.87x (the FL of the telescope is 506mm);
5 1930mm 3.74x (2.05x compared to 1).
This should be a result from 2 causes:
- the use of the BS barlow after the PMW;
- the PMW are at shorter distance to the sensor than it should be.
I will have to do more tests to see if with the correct distances the magnifications result as expected.

The photos are not cropped, just resized to 1200p, all with the same quality % to fit file size.

No problems with focus, being that the scope has 65mm focus range.

Remirath,

I ordered it directly from USA.
You should go a little further and reach S. Jacinto but not during this period - better from October to March - early February is my "photo season" there...
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Old Friday 29th April 2011, 00:20   #8
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I noticed that with not so good light increasing magnifications can limit resolution due to ISO increasing. The Garganey photos were taken at the end of the day when light was becoming a limiting factor. The NEX5 has a good high ISO performance but there are no miracles. I remembered to crop all originals to the same area, processing then with similar options at GIMP and show you the results...
The photo resulting from the "3x" has less light because auto ISO only goes to 1600. As the NEX5 has a tendency to overexpose I reduce the exposition 0.3 but it might be better to reduce a little more since this last one also show more detail/contrast. It went also to fotos at pt-ducks...
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Old Saturday 30th April 2011, 06:42   #9
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David, you are human like me. We do not have Bionic Eyes... Still thinking about how to get better focusing.... Thanks for sharing.

Another thing. How do you find focusing with the LCD? Even with A550, I still can't focus with Live View, even with 2X view.
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Old Monday 9th May 2011, 11:12   #10
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Thanks for the reply David. Could you post the link of the store where you bought it??

Regards,
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Old Tuesday 17th May 2011, 00:06   #11
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Alphan,

The NEX5, in manual focus, has a button to assist focus, increasing 7 or 14x, so focus is easy. Well sometimes it's a bit difficult to find the eye of the bird to focus it properly...
I think I have to purchase a release cable since I'm working with high magnifications and would be nice to decrease the speed when it's not needed to avoid being always at high ISO - some photos show shake from pressing the firing button...

Remirath,

The link is http://www.siebertoptics.com/Siebert...Wheel%20Barlow but the link for the PMW is not working - you have to ask to the contact e-mail.


Meanwhile I did some changes in the order of the T extenders and I reached 2.7x zoom - higher than that I loose one of the limits of magnification since the 65mm focus range of the telescope don't allow more.

I enclose some photos of the ends of magnifications
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Old Tuesday 17th May 2011, 00:10   #12
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More 2 examples. I have to clean the sensor...
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Old Tuesday 17th May 2011, 08:55   #13
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One thing in your images David, as the mag increases the F stop also increases and this then starts to easily show dust on the camera sensor which is showing in your posted images.

The basic test for checking the camera sensor is to put a lens on the camera and take a photo of the sky at something like f22. With the scope at approximately 2.5X we are approaching those sorts of F values so it's something to be wary of. The sensor needs to be spotless at higher mags.

edit - sorry, just noticed you said you need to clean the sensor.

Paul.
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Old Saturday 21st May 2011, 23:59   #14
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Hi Paul,
Still didn't clean the sensor but did some more tests when going to do some Flamingo work...

Alphan, today I remembered to use the 10 seconds auto-firing that takes 3 photos. Also noticed that with the manual focus help we can move the screen area to where we want ... In the flamingo photos I focused the rings. No crop.

The Marsh Harrier was taken at more than 200meters - about 200m measured on GoogleEarth but taken down hill. Crop to 25% on the first. Crop to 50% and scaled to the same pixel dimensions on the second.
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Old Tuesday 24th May 2011, 02:04   #15
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David, the higher magnification for focusing can be very useful but you need a real solid tripod to do that. I often find my 2X MF Focus check almost impossible due to the viewing of LCD under daylight and the constant slight shaking of the tripod.

I tried the 10sec X3 shots shots on my A230 quite frustrating as the 10 s seems like eternity LOL. Sometimes it came out blank (no birds) as they're long gone by then ... My A550 I would rather hook on the cable release.
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