Current Imaging Rig- 2012.01

By | November 28, 2017

Check out these 4 WHEEL ADAPTERS images:

Current Imaging Rig- 2012.01
Image by fractalSpawn
A lot of times showing my astrophotography begs the question, "what did you use?" So I set everything up to answer just that. 😀

Mount: …………………… Losmandy GM8
Main Scope: …………. Astro-Tech 90EDT
Main Camera: ………. Modified Canon XTi (400D)
Guiding Scope: …….. Orion ST8
Guiding System: …… SBIG ST-4
1 Sun X-tender 53Ah AGM deep-cycle battery
1 generic 18aH AGM deep-cycle battery

– – –

Below are some notes for those interested in one or more pieces of this setup. I’m speaking purely from an amateur astrophotography standpoint. For visual use, this mount would be able to handle a bit more weight and perform much better in a similar setup than I may make it seem. Cameras are much more discerning ‘observers’ then we humans are.

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The Mount:
. . .
The GM8 is a great mount, but I’m definitely pushing the imaging weight limit of this guy. The stated instrument weight limit from the Losmandy site is 30 lbs. For imaging, the rule is "half the limit to be safe; 2/3 is pushing but doable". That rule is very apparent here. The larger scope is about 13 by itself and combined, the scopes, rings, cameras and adapters weigh about 20-21~22 lbs. It is still very sturdy but doing an accurate balance is tricky unless the axis’ are ~perpendicular. Also, a reasonable gust of wind can shake it a bit. But we’re talking a GUST, not just a light breeze. I’ve imaged in light breezes with little problem.

The mount is not computerized ("GOTO") so I have to ‘PUSHTO’ my targets which can make finding things you can’t see, very difficult. While it can’t find anything, it does track automatically. Tracking is always on, and is working as soon as you’re done pushing to a target. Very ‘worry-free’.

As far as tracking accuracy; it does okay. Back before the ST-4 I was manually guiding using an illuminated cross-hair eyepiece. The guide star would be quite still for some few seconds, then it suddenly starts to move to one side, then the other. If asked to graph, it would look like a heartbeat type pattern. This made me learn to drift align to make sure that error didn’t also affect the ‘up and down’ movement of the guide star (DEC drift).

While the worm gear systems are much better than the CG5 I sold, there is still some work that needs to be done to get them adjusted just right. There are numerous websites discussing the motor/gear reduction/worm gear weirdness of Losmandy mounts, so you can find out more there. For this mount, I like to clean and re-lubricate about once every 15 mos, so the first time out with it can be tricky. After maintenance, I like to give worms on both axis’ an entire rotation by hand (very long and painful on the fingers) to make sure everything is smooth. When it’s cold, the worm and wheel can bind up if you don’t leave enough backlash, but I don’t really notice this amount when guiding and switching directions. It’s still pretty responsive. The ST-4 is able to ‘drive’ this mount quite efficiently. If you will or do have this mount, consider purchasing the Ovation one-piece worm block. There is too much play with the two individual worm blocks that come standard. If I weren’t upgrading soon, I would get these right away.

I like this mount, but because I’m already pushing the weight limit, I had considered upgrading to the bigger G11 and continue my loyalty to the brand. It will hold double the weight so I would be good for any future telescope/camera combination, but in the end I decided to aim for the top and start saving my pennies for an Astro-Physics Mach1GTO. AP states the weight at 45lbs, but AP is notoriously ultra conservative on their limitations (which I’m pretty sure are imaging limits). Physically, it’s a bigger mount so I would expect it to handle the same as the G11 with little trouble.
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Main Scope:
. . .
The Astro-Tech 90EDT is a heavy scope. Great optics but heavy and large for it’s size. It’s often mistaken for a 100mm or 110mm scope. It’s bigger brother, the AT111EDT is pretty much the same girth, but longer. I’ve thought about exchanging it to a more normal 8lb 90mm triplet. or keeping the same weight and getting a larger aperture reflector, but I like the scope and don’t think it’s worth replacing just yet.

This scope is great really, except for the focuser. I may have gotten a bad sample, but my micro-focus doesn’t really work with heavy stuff or with the focus lock on at all. I’ve noted the focus point so I’m focused after a few test shots and it’s not really being used all that much, but still, it should work better. I’ve also had to loosen the focuser attachment to the scope to get it working. The downside to that is it now moves forward and back just a couple of mm when you change directions. But again, I don’t use it so it’s not a big problem.

The optics are great. No false color that I can notice and I’ve imaged and looked at the moon several times with this. You can see from my moon photos that there is color on the moon, but no fringe color around the moon’s edge. A bit of field curvature but the Astro-Tech Field Flattener fixed that up perfectly. The images speak for themselves.
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The Guide System:
. . .
The Orion ST80 is nice and light. Since it’s only a fast doublet, it does have quite a bit of false color, but that doesn’t matter for guiding. It’s faster than the main scope at f/5 (main scope at f/6.67) so I need to use a Barlow lens to make guiding worth it. The rule is that you want to guide at twice the magnification of your imaging scope. This way the guider sees the movement and fixes it before the camera picks it up.

The ST-4 is awesome. Considering they were made in the early 90s and are still around say a lot. It is a finicky little bastard, but once you get to know it, it can be your best friend. Being the first stand-alone guiding system, you do not need to bring a computer along. Being somewhat a minimalist, I like not having a computer unless absolutely necessary. It’s also just one more thing to have to worry about powering or charging in the field.

My biggest problem was finding, focusing and using the right guide star. Because there is no display from the CCD, it’s hard to tell what it sees. I removed the flip mirror from the main scope and put it here so that I can use my old guiding eyepiece to help me find and center a good guide star. Adding the end of a Barlow lens to the camera nose-piece increases the magnification but it made it hard to get my illuminated eyepiece far enough inward to reach equal focus. After many attempts at it, I ended up removing about 4mm from the flip mirror ep barrel. They’re close enough now that I can use the EP to center. Since the EP is slighly out of focus when the guider is in focus, the star looks like a disc which makes judging appropriate guide star brightness easier to do.
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Miscellaneous Stuff:
. . .
An intervalometer (special timer) allows me to set the number and length of exposures so that I can just "set it and forget it" for a given target. In conjunction with the ST-4, they help me get some sleep or socialize with other astronomers.

The batteries are awesome! I had to learn a lot about batteries to get the right one, but I like the sealed AGM ones because they don’t spill, they don’t offgas when charging, I don’t have to fill with water, etc. They are expensive, but the Sun X-tender is built for military and government solar power installation systems so I know it’s going to last. Next on the wish list is a solar panel to charge when not at home. Using both the ST-4 and GM8 on the 18Ah battery gave me about 6 hours of use, and about 5 in winter. Now, I use the 18Ah battery for the mount because it only draws 500mA so it will do fine for a 2 nighter. The ST-4 draws 2 Amps so I use the 53Ah for it. I can go a full weekend and probably up to 4 whole nights with it before it needs charging.

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Power and Misc. – Case
Image by fensterbme
This is my case that carries all of my power gear, cords, chargers, as well as some cables and a few lighting items such as the reflectors among a few other odd things.

The Case is a Pelican 1510 case (with wheels) and above the case is a Westcott 42" 4:1 reflector kit. Items in the case include:

Paul C. Buff Vagabond II portable power pack.
7" stock reflectors for White Lighting X1600 strobes
Battery Charges, and adapters for AA chargers, Vagabond DC connetions, etc.
AV Cords for Canon HV20 Hi-Def camcorder
Power cords for lights and extension cords and power strips for distro’ing power between pack/lights and the location power.
Joby Pod SLR Zoom mini tripod.
Sync cords (in case PW’s don’t work for some odd reason), etc.

Marlin, And His Crawler Truck
Image by Visual Artist Frank Bonilla
Marlin Czajkowski, of Marlin Crawler fame, and his 1980 Toyota Crawler Truck. If you own a Toyota 4WD truck, or have ever been on the Dusy-Ershim or Rubicon Trails in California, then you have heard of Marlin.
Here is a description of his truck, from the website:

Marlin has been wheeling his 1980 Toyota Hilux Minitruck since 1983 when he became it’s second owner. Pictured above, his truck has evolved into the Ultimate trail and recovery rig. Basic specifications include the following:

1996 Toyota Tacoma 3RZ-FE 2.7-liter 4-cylinder engine, Turbo R151F 5-speed transmission with 5.15:1 1st gear and 3RZ-FE R-series conversion bellhousing, Triple Marlin Crawler Ultimate™ Overkill™ 23-spline MC08 Billet Double Roll™ Adapters with 2 sets of Total Spline™ 4.70:1 low range gear sets for a final Crawl Ratio of 1,372:1, Marlin Crawler 4" suspension Trail Flex system, ARBs front and rear, high pinion front differential, Alloy-USA Chromoly axles and UM06 Birfields, 37×12.50×15 Goodyear MTR tires on 15×10 Beadlock Specialties Beadlocks, and Full Marlin Crawler Body Armor.

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