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Topics - cardcudeflee

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I recently decided to go for it and purchased a Celestron AVX GEM mount as I had gotten about as much as I could out of using Alt-AZ mounts and short exposures. Unfortunately my preferred viewing location on my property has a limited view from North to South East and the view to the West is completely blocked by trees. When using calibration stars on the same side of the meridian as the stars I selected for alignment the GoTo seems to be fairly accurate but I still cannot get shots longer than 20 seconds if I'm lucky. The other night I could actually just about make out Arcturus through the trees and tried using that as a calibration start but I was way off and couldn't get a decent exposure longer than 5 seconds.

Any suggestions on how I can get a better polar alignment or what to do about calibrations stars? I am going to try setting up in my driveway weather permitting as I have a clearer view to the West there the only problem being I'm then surrounded by street lamps on both corners of my lot.

I attached an image of M31 taken with the new mount, 29 20 second exposures at 1600 ISO using an unmodified Canon 1000D and an Orion ED80 refractor for a 9 minute 40 second exposure. Still working on the processing skills. :-)

Thanks!


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Hello Friends,

I recently purchased an ES 16 dobsonian as my lightbucket for dark sites. So far, I am loving the scope. However, it will not work as a grab and go. I live in an apartment in Glendale CA, and I can view on the roof. There is a lot of light pollution and many lights on the roof. Due to these factors, planets, lunar and very bright DSOs would be my only real targets. I am considering a 4 inch APO. But by the time I purchase the scope and mount, I am going to be between $1K and $2K. Although I love the 3D effect of an APO, I am not wondering if an 8 inch dob, using a small cart to transport might be just as easy to set up and give me better views. My biggest concern is that I am 6'3" and I do not want to stoop over constantly. I have an adjustable viewing chair I used with my old Zhumell Z12. But that scope was at least 6 to 8 inches taller than the 8. So, I am open to suggestions. I am wondering about the Zhumell Z8, Skyline 8 (I believe they are the same scope) or the XT8 plus (about 8 lbs lighter). I would like to have an 8 F7 or F8, but I do not think that is possible unless I want to pay BIG BUCKS, which I don't.

My primary concern is the difference in cooling time and due to thermal issues on the roof, I believe the apo will handle the conditions better.

Please let me know the advantages and disadvantages of the dob vs apo.

Thanks and clearest of skies!

Mike

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Beginners Forum / Dark Skies & Rattlesnakes
« on: December 28, 2017, 11:14:24 PM »
While the rest of my family was taking in Saturday evening football games, my 7-year old son Andrew & I ventured out to the country in search of dark skies. Before the trip we visited www.lightpollutionmap.info to get advice on the darkest sky that's reasonably close to where we live. So we loaded up the car, jumped in and off we went. We got to a spot in about 30 minutes, a turn off a 2-lane highway to a gravel road. We drove about 50 yards until we came to a ranch gate, quickly unloaded and setup at the tailgate of my wife's Ford Escape. Immediately upon getting out of the car we could see the Milky Way. Great start. In no time, we had the Andromeda galaxy (M31) in the eyepiece. We have an Orion XT8, with an Agena 2-inch 38mm SWA eyepiece. M31 definitely looked better here than at my house, but I will admit, I believe we're still looking at it too big (31x). I've read that M31 is at its best at 20x. Anyway after taking it in for 10-15 minutes we heard a rustling in the nearby trees. It spooked me and my son, so reluctantly I turned on my iPhone's flashlight. I couldn't see anything in or around the nearby trees or brush but an unwelcome guest quickly came into view about 10 feet from the car... a 4+ foot eastern diamond back rattlesnake. I thought it was a chicken snake at first, but Andrew nailed it stating, "Dad that's a diamondback rattlesnake." This kid watches Coyote Peterson's YouTube channel and generally knows his stuff. I assumed his imagination was getting the better of him and I crept in to take a closer look. Upon doing so, the head and markings became clear - Andrew was spot on. The rattler was hard to see. I had to turn off the flashlight to get a photo (which was unsettling). To make matters worse it was slowly creeping towards the car. We loaded up quickly and left, no injury, no problem. On the way home, Andrew mentioned that had we not heard the noise in the nearby brush, we would not have turned on the lights to investigate. After all, we wanted to acclimate our eyes to night seeing.This was our first Dark Skies trek. Lesson learned.

We got lucky, but it begs the question. Is there a checklist out there or a guide to safe outings? My brother suggested snake boots. Anyone else got any suggestions, close calls, or mishaps to share? We're looking for awareness & preparation, tips, do's & don'ts - to keep it fun and safe. Photo of the 'guest' attached.

Mike Fulbright
Waco, Texas


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General Astronomy & Observing / Planning an astro setup to beat floaters
« on: December 27, 2017, 12:44:47 PM »
Hello guys,

I'm 31 and slightly shortsighted, I had an onstet of floaters at around 17, then they stopped anoying me until a year ago when I had another onset, they are particularly bordersome on my left eye, which is my astronomy observing eye.

I went to the oftalmologist last week and the Doctor prescived me a pill suplement conteining lutein, zeaxantine and other antioxidants. He also prescibed Diclofenact sodium eyedrops for a month. Aside from that he said there is little more than can be done.

I've noticed that floaters where specially prominent with my 80mm f6 APO using a Quark eyepiece (f25 with quark) for solar observations as opposed to in my 14" f4,6 dobsonian, so I've done some googling, I'm compilling the following assumptions (but would be great if you guys could verify them):

A -Floaters increase as exit pupil decreases, going below 0,4mm exit pupil is not recommended as per Televue Website and going below 1mm is not pleasant as per my experience.

B -Floaters increase as aperture decreases

C -Floaters increase if light increases, this is consistent with my everyday experience, so a neutral filter for brighter targets such as the moon could help.

D -Floaters can be eliminated by the brain in binoview mode, the 50% reduction in light could also help.

E -Floaters are not related to the scope central obstruction (again, I'm not sure).

So according to these assumptions, I presume that:

1-The bigger the scope aperture the better to beat floaters, scopes with big obstructions like SC could be good in that particular aspect as some of the light is lost by the obstruction.

2-Big AFOV eyepieces are not to be recommended as the goal would be to enclose the object with the biggest exit pupil possible.

3-Binoviewer is recommended.

4-Faster telescopes are preferable to slower telescopes (again, I'm not sure about this).Since I won't be using my dobsonian anymore (as it will be stored at my permanent observatory), I'm leaning towards buying a CPC11 EdgeHD with binoviews and TV plossl.

Would that setup work well?

Known formulas:
Exit pupil = eyepiece focal length รท telescope f/# (from televue website)

Unknown formulas:

Floater prebalence= exit pupil and brightness (could anyone share their thoughts as how to find this personal relationship?)

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