Category Archives: Readers’ Requests

Jim’s responses to readers requests received by email, or from Scope Out or AstroLog.

What do I think of the OMEGON LX3 Tracker?

I received this question after posting Three Comets to Flickr, and after posting associated discussion here about the Omegon LX2. I was not aware that Omegon had released an LX3, I had to see how the two devices compared. My comparison is based upon my actual experience with the LX2, and with what I was able to glean about the LX3.

I have written about using the LX2 in two articles: Have I Ever Seen Two Comets in the Same Photo?, What Tracking was I using for Three Comets? I have also posted another image that used the LX2 in Flickr, Milky Way and Meteor with Jupiter.

The LX3 has an optical polar alignment finder where the LX2 uses a short plastic tube (more like a straw, because there are no optics). I am certain that the LX3 can be aligned more accurately, and maybe that will be more important at longer focal lengths than I have used with the LX2. I shot Three Comets at 55mm after aligning through the “straw” and the tracking looked great.

The LX3 has 60 minutes of tracking vs. 30 minutes for the LX2, which is a very nice improvement. This is important, because after the timer runs down, rewinding it moves the camera back to where the it was pointing 30 minutes ago. This means that the camera must be repointed at the star field before proceeding. Fortunately, I only wanted 30 minutes for Three Comets, because I wanted to avoid the thicker, wetter atmosphere closer to the horizon.

Improved tracking accuracy and payload capacity – I cannot speak to these. I was, however, intrigued by idea that the LX3’s clockwork ticks per minute can be measured to assess tracking accuracy at various spring tensions. Similar to the LX3, the LX2 has a spring that can be set to support heavier loads. I think that I will measure my ticks with various lenses.

That’s about it for comparison. As for Omegon LX3 being worth the extra money over the LX2. I would say that it depends. Thirty extra minutes of tracking is awefully attractive!

© 2021 Jim Johnson

What Tracking was I using for Three Comets?

Here is the extended question that I was asked shortly after posting Three Comets:

It was fun to watch you that night.  Your preparation truly paid off in a stellar way.  What tracking were you using with your Canon?  I have no experience with or software for stacking images.  On Saturday, I pushed my 14mm lens to the limit with 25 second exposures without star trailing when pointed south.  With that lens, I’m able to use a lightweight travel tripod with no tracking.  I’m considering a 70-200mm lens for my Nikon D750 for astrophotography, but I’d still like to be relatively lightweight and portable (carry on).  Suggestions?

And my answer:

Thanks, I am glad that you had fun watching me struggle and sweat with that one. 😎

Actually, I am pretty sure that I had the most fun working on this image.

My Canon was fitted with a 55mm f/1.4 lens that I had stopped down to f/2.8. It was tracking on a $160-ish mechanical wind up tracker made by Omegon. It is called an LX2 Mini Tracker. 

For anyone who already has a DSLR and a couple of lenses, this device is hard to beat for anyone wanting to get started in astrophotography without a huge up front investment. I wish that my Losmandy G-11 tracked as good as this tracker does…feel free to open the image and zoom in. There are no elongated stars in forty seven 25 second exposures. So that’s my suggestion for a tracking device. The tracker is small and lightweight, so it is perfect for travel.

I am pretty sure that I would have gotten elongated stars if not for the tracker. The tracker runs for about 30 minutes on a wind up (like winding your watch), and I got star trails in some frames after it timer ran down at the end of my run.

Stopping to reflect for a moment while writing just now, I realized a few things. This is an exception image, but it was not just me. This is a HAL image.

Acquiring the kit that I have to do this imagery, wider FoV camera lenses and the tracker, was inspired by Cheryl’s wide field imagery.

The image would not have been possible without Victor and Bob opening Carrs Mill both nights this weekend, or without my good fortune to be a member and and having access to this incredible resource.  Of course, there have been many HAL members opening the park over the years, which has given me the opportunity to learn the astronomy arts.

I have been inspired by Brad, Gene, Ken, James, Steve, John, and HAL’s many other top-notch astrophotographers. Additionally, people like Gene and James have inspired me to work carefully and take my time and read the literature on any new software that I might to use. 

Last, and certainly not least, without what you and the HAL Board (and past boards have done) does month in and month out to keep HAL vibrant and relevant, there would be no HAL to make this image possible.

I am very grateful for being a HAL member, which has having been in the right place at the right time for grabbing the torch and running with it.

© 2020 Jim Johnson

Have I ever Seen Two Comets in the same Photo?

This question came to me from a neighbor during a discussion in July 2020 about an image of Comet NEOWISE (C/2020 F3) that I had recently posted. My recollection at the time was that I had not seen such an image. A few weeks later during a Saturday morning breakfast discussion with some astronomy friends in early August, I learned that two comets would be aligned as such that they could be seen within the same camera frame, so I set about to produce an image of two comets.

The star of the two-comet scene was NEOWISE which had dominated astronomers’ attention during the entire month of July 2020. By the second week of August, however, NEOWISE had faded to magnitude 7.6. At this point it could only be seen with telescopic magnification. The other comet was PANSTARRS (C/2017 T2) at a much dimmer magnitude 10.7.

As luck would have it, as I was looking for these two objects’ placement in Stellarium, I noticed a third comet, Comet Lemmon (C/2019 U6) at magnitude 10.3. It was significantly farther from NEOWISE than was PANSTARRS, but I could still fit the trio into a single camera frame using a 55 millimeter camera lens.

Luck still staying with me, the three comets were located in a star field that included Arcturus and some other stars that would make it easier to identify the star field while I was working at the camera, even if I could not actually see the comets. I was counting on post processing to make them visible in the image.

The same day that the breakfast discussion had occurred, one of Howard Astronomical League’s dark observing sites was opened for its members, and I went out on my first attempt to image the three comets. I set up with my Canon 60Da mounted on a Omegon LX2 Mini (mechanical wind up) tracker. I had not used this device for some time, so I found myself fumbling with it way too long. By the time I was polar aligned, had the target framed, and decided on the exposure, I was exactly one hour later than I had hoped to start imaging. By then the comets were very low in the mucky part of the atmosphere, and ground fog had started to appear. I did not have a dew heater for the camera lens, so it was completely overwhelmed by moisture.

While still in the field, I was able to see NEOWISE in my unprocessed images on my dewy laptop screen, and I was able to verify that I was capturing the star field that contained the other two comets. Even though I could not see the comets in these images, I was hopeful that I would be able to pull them out in post-processing. My luck had run out. In processing the next morning, I found that I did not have a useable image of the three comets.

Amazingly, we had another lucky break in the clouds, and the site was opened again the next night night. I added a battery and dew heater to my pack up, and headed out again. Equally as important, I spent some time reacquainting myself with the tracker in the clear light of day. It was another very moist evening, but not nearly as challenging at the night before. Because I was not fumbling with the tracker, I was able get up and running and was shooting sub-frames as soon as it was dark enough. I could see right away that my data quality was much higher than the night before. I couldn’t see the other two comets, but I saw enough stars that I was pretty sure that I could pull the other two comets out in post processing.

Getting the image that I wanted out of the data that I had captured the night before required that I stretch my processing skills to the limit, but somehow I managed. Not only was I able to see the two dim comets, I cross checked against Stellarium to verify that the two green blobs were indeed Lemmon and PANSTARRS. Here is the Three Comets image that I posted to Flickr.

I must add that I am pretty impressed with the tracker. Of the fifty sub-frames that I shot, I threw away only one for a tracking issue. Not bad for a $200, low-tech wind up device?!!

Technical information for Three Comets: Canon EOS 60Da with 55mm lens at f/2.8, and mounted on a Omegon LX2 Mini Tracker. Twenty minutes total integration time in 47 x 25 second light frames. Calibration frames consisted of 25 dark frames, 25 flat frames, and 25 flat dark frames. Light frames and calibration frames were stacked in Deep Sky Stacker, and post-processing was done in Photoshop.

© 2020 Jim Johnson

Recommending a Telescope

Q: I have a Canon 5D. Any recommendations for a compatible telescope?

A: You have a high-end camera that deserves high-end equipment. I am so happy with my first telescope/mount combination (TeleVue NP101is/Losmandy GM8) that I continue to recommend it four years after I purchased it. Ultimately, selecting a telescope is a highly personal proposition, and your budget and anticipated uses will determine which is THE right telescope for you. There is a lot of worthwhile material on the Web about the best telescope for particular application.

Here are links to some posts that provide a sense of how I have thought through some of my selection decisions:

Jim’s Astrophotography Equipment
Getting over Aperture Fever
Trying Out a Used Celestron C11
Rationalizing a GOTO Telescope Mount
Finding Barnard’s Star
Planning to Build an Observatory

© James R. Johnson, 2015.

Photo the nearest star and let us know about it

I managed to do the most important thing that I wanted to get done last month:  respond to a reader’s request. The request was quite simple – “photo the nearest star and let us know about it.” There are seemingly thousands of stars that can be seen in the sky, so one might think that a nearby star would be a bright and easy target. Surprisingly, the closest star that we can see from our northern latitudes is a rather dim star that can only be seen with a binocular or telescope. Increasing the challenge, it is located in constellation of rather dim stars. And finally, Barnard’s Star is in a constellation that will soon be below the horizon before sunset as the Earth continues its orbit about the Sun, so I had to rush to get this project done soon or wait until next summer. My first attempt was on a relatively clear evening, but the nearly full Moon made it difficult to positively identify the star field that I was seeking, and clouds eventually set in before I could complete the mission. The next time that I was able to get out, there was no Moon and no clouds, but I did not succeed in locating the target before that area of the sky set below the horizon. By the third time that I was able to get out, I had revised my search technique, and I quickly captured an image of the correct star field on my first attempt. Here is a link to the result of my work:

Astronomy-related Gift for an 11-year Old

Q: My nephew William (11 years old) loves astronomy and I remember you saying that you love teaching kids about astronomy.  Any suggestions of things out there on the market that could be cool?

A: If you want William to be the envy of me, and almost every other amateur astronomer on the planet, shell out $20K and get him a Meade 12″ LX200 OTA, Losmandy Titan mount, and an SBIG ST1100. Short of that, there are a lot of cheap (low cost, low quality) telescopes and binoculars out there that might be tempting, but I would avoid them as they usually lead to disappointment. Worthwhile equipment, even entry level, is too expensive for an 11-year old, so what’s left? I think an age-appropriate book. Try Amazon and search on “astronomy for kids.” You can pick your price range with a single item or by picking a few. Given that he is a boy, and already interested, I would avoid the “cartoony” books and go for something more realistic, with real photographs.