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M20 Trifid Nebula in LRGBHa

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Posts Made By: Wei-Hao Wang

September 20, 2004 09:57 AM Forum: Film Astrophotography - Imaging and Processing

First light -- Mamiya 645 300mm f/2.8 APO

Posted By Wei-Hao Wang
Hi Todd,

This is a great mosaic image! 300/2.8 is a nice lens. I have Mamiya 645 and 200/2.8 but never got good pictures like yours. There is always some flexure problem with 200/2.8. It's a shame that it doesn't have a tripod connector!

I saw somebody use 300/2.8 on a 6x7 film holder. The 6x7 frame is nicely covered by this lens even at F2.8. I believe you can use this lens wide open. Please take more pictures like this.

Wei-Hao

September 26, 2004 11:43 AM Forum: Film Astrophotography - Imaging and Processing

NGC 1499 or California Nebula

Posted By Wei-Hao Wang
Hi Augie,

Is your field flattener the 4" version or the 2.7" version? These seems to be quite lot of vignetting. The nebula does look very nice.

Thanks for sharing.

Wei-Hao

September 27, 2004 02:41 PM Forum: Takahashi

Alternative focal reducer for an FS102

Posted By Wei-Hao Wang
Hi Mike,

Are you going to use the reducer for visual or photo? If for visual use, have you considered a longer fl eyepiece?

Wei-Hao

October 8, 2004 09:50 AM Forum: Film Astrophotography - Imaging and Processing

M-31

Posted By Wei-Hao Wang
very beautiful.

November 6, 2004 06:52 AM Forum: Takahashi

Focus issue with camera angle adjuster

Posted By Wei-Hao Wang
Hi Mike,

It's odd. The camera angle adjuster is designed to be used with the focal reducer.

According to the system chart of FS102
( http://www.takahashijapan.com/Chart/Tube/102npe.jpg ),
there must be an extension tube called CA-35 (#30 on the chart) between the reducer/flattener (#18) and the camera mount (#33). Do you have this? (#6 on the chart is the camera angle adjuster.)

Wei-Hao

December 7, 2004 01:18 AM Forum: Film Astrophotography - Imaging and Processing

Pentax 6 x 7 battery

Posted By Wei-Hao Wang
Hi,

A new battery should be enough for one night of long exposures. If you want to get rid of battery problems totally, you can use this:
http://www.sciencecenter.net/hutech/pentax/battelim.htm

Wei-Hao

December 20, 2004 12:49 AM Forum: Film Astrophotography - Imaging and Processing

Achromat technique: RGB photography...

Posted By Wei-Hao Wang
Hi,

I highly doubt if a filtered achromat can be as good as an apo.

One example is the recent discussion in the Astro-Physics forum in astromart, "Color curve comparison." You can look at the figure of the first article in that thread. The focus difference between the 0.486 um and 0.405 um lines of the achromat is many many times that of the APO. These two lines are both blue. They will go through the same broadband filter and cannot be focused at the same time. On an achromat, it's not just that blue light has a focus different from green and red. Even blue light itself has a very wide range of focus. (Well, this may be solved if you use nerrow-band filter.)

Wei-Hao


March 23, 2005 10:59 AM Forum: CCD Imaging and Processing/Deep Sky

M65 and M66

Posted By Wei-Hao Wang
Hi Jim,

This is a great image, especially knowing that it's taken by ToUcam. I noticed that the background brightness is not quite uniform. Do you think it is a flat field effect?

Wei-Hao

March 29, 2005 08:50 AM Forum: Film Astrophotography - Imaging and Processing

A way to make prints from slides

Posted By Wei-Hao Wang
Hi,

Indeed, this technique doesn't just apply to slide, it applies to negatives as well. You can use side film to duplicate negatives. In the duplicating process, both color saturation and contrast will increase. You can even push process the slide to make the contrast increase more dramatic.

Wei-Hao

March 31, 2005 01:10 AM Forum: Film Astrophotography - Imaging and Processing

Which slide film do you use?

Posted By Wei-Hao Wang
Hi,

E200 is good. Indeed, E200 has been the primary slide film used by astrophotographers in the US, not E100S. E200 has good red response but relatively poor blue. Fuji Provia 400F has better balanced red and blue.

Cheers,

Wei-Hao

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