Best Astronomical Tracking mount and lens and technique

[brian_hirschfeld]

<p>I am interested in trying out some astrophotography this summer, and I was wondering what the best astronomical tracking mount is....I have a Nikon D700, 14-24mm 2.8, 24-70mm 2.8, 80-400mm 4.5-5.6, Pre-ordered 24mm 1.4, 50mm 1.4, 85mm 1.4 and a 60-105mm macro, I was wondering what I should use/ what I need to get, I think a astronomical tracking head is needed but I am not sure...I really liked this picture that I saw: http://www.redbubble.com/people/mikesalway/art/2175663-2-the-milky-way-galaxy <br>

Also I was wondering about the five exposures were they done with Ev -2, -1, 0, 1, 2?</p>

[avery1]

<p>http://www.photo.net/nature-photography-forum/00SErk</p>

[MichaelChang]

<p>Hi Brian, I take it from your question that you'd like to attempt the picture shown. The link Avery pointed to is probably more suited for long focal lengths but contains useful information.</p>

<p>You'll need an eqatorial mount. This can be anything from a home-brew manually operated barndoor tracker to full-fledged automated mounts. They will all do the wide angle shot that you linked to.</p>

<p>Additional considerations:<br>

1. Find a location with very dark skies.<br>

2. Learn how to polar-align the mount with sufficient accuracy.<br>

3. Learn how to stack and process the acquired images. </p>

<p>Typically it'll take lots of planning and exercises with anticipated technique and it looks like you have the right gear.</p>

<p>A basic manually operated Scotch mount you can build: <a href="http://www.philharrington.net/scotch.htm"><Link></a><br>

A table-top mount which you can motorize: <a href="http://www.telescope.com/control/accessories/mounts-and-tripods/orion-min-eq-tabletop-equatorial-telescope-mount"><Link> </a><br>

A mid-size mount, more heavy duty: <a href="http://www.telescope.com/control/accessories/mounts-and-tripods/orion-astroview-equatorial-telescope-mount"><Link></a> or <a href="http://www.telescope.com/control/accessories/mounts-and-tripods/orion-skyview-pro-equatorial-telescope-mount"><Link><br /></a><br>

As to your second question, I think the picture is a composite of 5 images of the same exposure, reason being:<br>

1. To eliminate the cumulative tracking error of the mount.<br>

2. To minimize camera related issues - battery life, sensor blooming.</p>

<p>Final point; although you can do in-camera noise reduction, it's much easier to obtain a separate 5 minute dark-frame and do the subtraction in software. </p>

 

[diane_madura]

<p>Michael, how do you do the noise subtraction in software? I don't remember.</p>

[leif_goodwin8]

<p>According to some sources Nikon cameras have an intrusive noise reduction algorithm on long exposures which removes dim stars:<br>

http://www.astrosurf.com/buil/nikon_test/test.htm<br>

The solution is to turn the camera off at the end of the exposure proper, during the NR stage. It's a shame as it means you can't use the in camera intervalometer when present.<br>

The five exposures are stacked. It gives a better result - less noise - compared to one long exposure. I assume they were all the same duration, with the camera in manual exposure mode.<br>

The Astrotrac looks like the smallest, most convenient driven equatorial mount. Astrophotography is not easy, especially in a cold country such as the UK, where frozen extremities and condensation are real problems.</p>