Originally posted by 2old4toys Anyone tried an equatorial mount used with a Pentax QS1 to shoot the Milky Way? Or is it a lost cause with such a small sensor...
Interested to hear from any astrophotographers pushing the limits using the Q 😅
Well in a few words: It ain’t the best!
In a few more words, ....
I went out on the evening of June 29 and took a bunch of Q7 shots of the sky, the last one followed a minute or two later by a couple more with my K-1. Both cameras went for a ride on my polar tracking mount, although that was hardly necessary for the wide field of view and exposure length I used.
The exposures used the same settings for both cameras: Manual, with ISO 400, aperture f 4.0, and exposure time of 30 seconds. White balance was daylight for both cameras, as well.
The Q7 had the 02 wide angle zoom lens on it, set at its widest: 5 mm focal length, equivalent to about 25 mm on full frame. For the K-1, I used my 20-35 mm FA zoom, set at 20 mm. In retrospect, I guess I should have set it at 25 mm, although that would not have made much difference.
The shots shown here were taken at about as late as I could go before local moonrise - around 9:20 PM local (standard time here in Arizona in the summer time). Even so, the K-1 frame is affected by the rising moon.
If all you want are wide field views showing the star clouds of the central Milky Way, the Q7 almost works. See picture 2 for the full field Q7 view (downsized to 1280 pixels across). Compared to the K-1 version (picture 3 below), the star clouds show up comparably. Both frames have been brightened and contrast enhanced in Photoshop Elements. The horizon appears tilted in these images because the cameras are aligned with the celestial coordinate system, courtesy of the polar mount. The celestial equator lies a few degrees below the top of the frames, and runs parallel to the top edges.
When you zoom in, though, the K-1 wins hands down. Pictures 4 (Q7) and 5 (K-1) show a zoomed-in area near Saturn (the brightest object, left of center in each frame). The field of view of each zoom is very similar, but you can see many more, and crisper, stars in the K-1 image. For the Q7, the limiting magnitude is around 6.5, whereas the K-1 goes to about 9th magnitude - a factor of almost 10 fainter. (The magnitude system is the astronomers’ backwards, logarithmic scale for the brightness of celestial objects - bigger numbers are fainter. A step of 1 magnitude corresponds to a factor of about 2.51 in brightness - more precisely, the fifth root of 100 for you mathematicians!) The Q7 limit is probably due to the higher noise in the Q7 images, even at ISO of just 400.
As soon as I set up, I (re)discovered perhaps the most limiting factor in using the Q7 for astro photography: the longest convenient exposure is only 30 seconds. There is a “bulb” exposure setting - BUT YOU CAN NOT PLUG IN A REMOTE CONTROL - there is no socket on the camera. The only way to get an exposure longer than 30 seconds is to hold the shutter button down by hand - not a good idea for long guided exposures!!! - or to use an infrared remote. Of course, you can always stack multiple frames, but that’s a pain!
I also discovered that the FA 20-35 zoom lens has an awful lot of coma flaring away from the center of the image at 20 mm zoom and f 4.0!
The first picture shows the diminutive Q7 perched atop my fairly hefty tracking mount and its home-made mounting bracket.
I was shooting both cameras in RAW+. If anybody wants the original RAW files (they are big!) to try their own PP, let me know.