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DataCable
2003-Sep-07, 04:40 AM
What with my amazement at catching sight of Mars next to the full moon via the ol' Mk-I eyeball, 2 weeks before opposition, I ordered myself a 'scope, the Celestron Firstscope 114EQ, specs of which can be found Here (http://www.celestron.com/prod_pgs/tel/fs114eq.htm). It arrived on the 27th. I also got a camera adapter for my old Minolta SRT102, thinking I'd like to get some photos. I have yet to make the attempt, though I should obviously try soon before the planets diverge too much.

With the 90x mag. from the included 10mm eyepiece, I can clearly define the disk of the planet, and if I look closely, make out a bright pinpoint of the polar cap. However, the whole disk is a bright, washed-out orange. Is this due to the un-filtered intensity of raw Mars-shine, or distortion from the atmosphere (or both)? Only last night was I able to faintly make out the maria. Would a filter improve the clarity any, and would a simple lunar filter do, or are colored filters preferable? I've seen descriptions of particular color filters bringing out certain details, but I'm more interested in an overall "true-color" representation, if that's possible.

On magnification: I'd like some opinions, which would be better: get a 4mm eyepiece, which would give me just-under-the-theoretical-maximum of 225x, or get a 3x Barlow and use it with the 10mm, resulting in supposedly-over-the-maximum of 270x?

On collimation: I didn't spring for a laser, only a cheshire for right now. I think I have things as closely aligned as I can get them, however it appears the focuser tube is a bit off. If I line up the crosshairs when the tube is fully retracted, the run the tube all the way out, the crosshairs are no longer lined up. It appears either the whole focuser assembly isn't square to the body, or the movable tube's optical axis isn't consistent with the axis of it's motion. I'm not quite sure how I'd correct this.

Here's hoping the skies here in NE Ohio are clear sometime around New Years, when Saturn is at opposition.

Pinemarten
2003-Sep-07, 11:04 PM
One the focuser alignment problem, you may be able to 'shim' one end of the focuser. It may only need a tiny one, a single strand of cat fur perhaps?

RichField
2003-Sep-08, 03:44 AM
DataCable,

I did try a lunar filter on Mars this past Friday. I don't have any other filters, so I don't have anything to compare it to. I was able to more clearly make out the polar cap with the filter, and I think some of the surface features. I actually don't remember whether I could see them or not, I knew at the time.

This was originally at 48x (10 in f/5 dob), definitely too small to make out surfaces features but I'm pretty sure I saw the ice cap. This was while switching back to Mars from the Moon which is why the filter was still on the eyepiece. Later I mentioned that I thought the lunar filter highlighted the ice cap and was asked to put it back on, this time at about 190x.

My recommendation for an eyepiece would be the 4mm EP over the 3x barlow given only those two options. However, I'd actually recommend a 2x barlow over both. Without actually checking the Celestron site, I'm pretty sure...good thing I did, I'd be wrong. I thought it came with at 25mm, it comes with a 20. I retract my 2x recommendation. If magnification is what you're after, I'd still stay under the rule of thumb limit. Otherwise, you might also consider a noninteger barlow like a 1.5x (I think I've seen these, or a 2.5x which I've definitely seen. That combined with the 4mm and the two original EPs should give a nice spread. Alternately a 2.5x outright would effectively give you the 4mm and an 8mm, but the price may be more than you want to spend. (It is for me)

Keep in mind that atmospheric conditions may limit the useful magnification on any given night meaning the highest magnification may stay in the box more than it's on the scope. I have the EPs to get up to 380x, but I've been most satisfied viewing Mars at just under 200x.
YMMV

Dickenmeyer
2003-Sep-08, 03:54 AM
I've been using filters off and on when observing Mars this summer and I have had mixed feelings about them. They do seem to improve the contrast a little tiny bit, Mars is so bright right now that I have even used my lunar filter with some success, but the improvement is real subtle. Speaking of subtle, the Martian surface features, excluding the polar caps, are just that. You are going to have to put in some eyepiece time and wait for those moments when you get a few seconds of good steady air for the markings to really stand out and the higher you crank up the power the longer you need to watch because you are magnifying the distorion caused by the air too. I would recommend sticking with your 10mm eyepiece and getting a good quality 2x or maybe 3x barlow. Orion and Meade both make good apochromatic barlows with practically no color distortion, I have one of each brand and they work great, what's more when you use an eyepiece with a barlow the eye relief of the eyepiece stays the same even though you have effectively doubled or tripled the magnification, whereas if you change to a shorter focal length eyepiece you lose some eye relief and your eyes will get tired faster.

skyglow1
2003-Sep-08, 05:31 AM
I found that while using my 4inch refractor on Mars, it was extremely bright will lots of glare. I could still see a tiny little bit of detail at 100x, but I found that adding my polarizing filter to the eyepiece really helped alot. You caould also try stopping down the telescope.

skyglow1

Charlie in Dayton
2003-Sep-08, 06:28 AM
Having wielded the other oar in the same boat...

Standard moon filters give too much of a greenish cast, although they're fine for cutting the glare. You need something neutral in color. Orion sells a variable 1%-40% polarizing filter. Or you could make one on the cheap...go to your local SuperCheapo store and ask if they have any cheap kids' polarized sunglasses. Grab a couple of pair, look at something bright, and cross the lenses. If things go dark, snag 'em, pop the lenses, and hold 'em over your eyepiece. Instant polarizer.

Check the supply houses like Edmund Scientific or the like...see if you can grab a few cheap sheets of polarizing material. There's a kit on there with lots of 1 1/2" - 2" sheets for about twenty bucks.

Alternately, try stopping down the aperture. I was viewing the Moon quite comfortably last night with my 5" stopped down to about 1 1/2". And I highly recommend the wider-field eyepiece in the Barlow trick. Much easier on the eyes. On my scope, a 10mm in a 2x barlow was a lot easier to live with than a straight 6mm...

mike alexander
2003-Sep-08, 11:53 PM
I've also been using a variable polarizing filter all summer and have been very pleased with the results.

DataCable
2003-Sep-09, 06:04 AM
Thanx for all the advice. I'll take it into consideration once I get my first set of test photos developed (hopefully tomorrow).

I just shot off a 12exp. roll of Kodak Gold 200, 6 each of Mars at 90x and the moon at 45x at various exposure times. I don't have a cable release (didn't think to order one along with the 'scope) so I relied entirely on the internal timer, knowing how this mount bounces about just fumbling for the adjustment knobs.

Tedious process: Center Mars in frame (actually offset it to the right knowing it'll move by the time I get set), cock shutter, flip up mirror, cock timer and release... wait for click... flip down mirror, step down shutter speed and repeat.

I started off on Bulb (which, with this timer, holds the shutter open for about 3.75sec.), then stepped through 1sec, 1/2sec, 1/4sec, 1/8sec and 1/15sec. I don't know if Mars will come out at all, but if it does, it'll only be on MAYBE the first few shots, and definitely leave a bit of a streak. I'm sure the moon will be blown out on the first few shots, as it was nearly full and filled almost the entire frame. Focus is a bit of a crap-shoot as well, as the focusing screen in this camera is useless at f/8.

It would've been nice to get a shot of the two at their nearest pass, but that'll be at about 9am here. Hawaii should have a good view of it, though, between 2-3am their time.

On cheap polarizing filters: I have a pair of old polarized clip-on sunglasses that are too large for my current frames (and I prefer driving tint lenses anyway). I tried slipping it between my eye and the eyepiece, but it's so scratched up, it was more hinderance than help. BTW, an alternative test for lens polarization I've stumbled on is to look through the lens at a digital watch (other LCD displays may work as well) and turn the lens 90deg. from normal orientation. If it's polarized, the entire LCD screen will black out.

Question: How does one stop-down the aperture of a telescope?

Pinemarten
2003-Sep-09, 10:08 AM
When using 200ASA film, I am curious as to how the 'grain' affects your photos.
I have never taken photos through a telescope, but I have been an amateur photographer (on and off), for a few years.
I like using the lowest ASA possible. I would assume that if the exposure time is not an issue, then the lower ASA films would yield better resolution in the final print/negative/slide etc. with telescope shots.
I bought a couple of rolls of 50ASA slide film once, and had them scanned into digital by a really nice (read expensive) machine at a camera store.
I had one frame scanned to a 26MB JPG file. When I open it in a good photo editing program and zoom in lots, the pixelation of the file shows up before the grain of the film.

DataCable
2003-Sep-09, 06:20 PM
Yeah, I went for the lower speed knowing that higher speed film is more coarse. I would've gone for 100, but they only had that in 24 or 36exp. rolls, and I just wanted to do a test with a small roll first to get some idea of valid exposure times. The relationship is proportional, right? Find a good exposure time for 200, then double it for 100, or quadruple for 50?

And to maybe answer my own question above, the cover for the open end of my Newt has a smaller removable cover in the middle, about half the diameter. Could that be used to stop-down the aperture? I couldn't think of any use for it until after I posted the last message, and the instruction "manual" doesn't say a peep about it. Although I realize this might result in lower quality (less contrast?), as the secondary mirror would proportionately obstruct a greater percentage of the aperture.

Film is at the lab right now, I'll let you all know how (if?) the pics turned out later tonight.

RichField
2003-Sep-09, 07:44 PM
And to maybe answer my own question above, the cover for the open end of my Newt has a smaller removable cover in the middle, about half the diameter. Could that be used to stop-down the aperture? I couldn't think of any use for it until after I posted the last message, and the instruction "manual" doesn't say a peep about it. Although I realize this might result in lower quality (less contrast?), as the secondary mirror would proportionately obstruct a greater percentage of the aperture.
It could be used to stop down the aperature, but just like you said, that's not the best place to put it on a newt. The secondary still blocks the same profile on the primary, but given the smaller aperture is now a larger percentage. Additionally, you still have the spider, assuming there is one, to produce diffraction spikes. A better solution is an off axis mask that reduces the aperture while missing the secondary and spider.

Just a guess but it could also be used for daytime collimation where image quality is not an issue, but I don't see a huge advantage to using the smaller opening, at least not as the only reason to design it that way. As a dangerous alternative, if this were one of those scopes that came with a solar filter designed to be used at the eyepiece, this could be to stop down the aperture for that, but I sure wouldn't try it. However, I don't think Celestron sells scopes with that type of filter.

Good luck with the photos.

Charlie in Dayton
2003-Sep-10, 01:50 AM
And to maybe answer my own question above, the cover for the open end of my Newt has a smaller removable cover in the middle, about half the diameter. Could that be used to stop-down the aperture? I couldn't think of any use for it until after I posted the last message, and the instruction "manual" doesn't say a peep about it. Although I realize this might result in lower quality (less contrast?), as the secondary mirror would proportionately obstruct a greater percentage of the aperture.

You got it, bubba...I used my 130mm that way last weekend at VOA Park to observe the Moon. Stopped it down right nice to maybe 40 mm or so in the little hole. Didn't even need a Moon filter, it worked so well. Am seriously thinking about whipping out a Baader solar filter just for the little hole. Legend has it that there's an ideal position relative to a clock face for the little hole in the dust cover, but I have yet to find anything on it. At least keep the hole so it's away from the spider legs or where anything else protrudes in the light path. (PPS Okay, I should read things closer...the hole in my dust cover is off center, almost to the edge of main aperture.)

I'm doing the 'choose the film' bit right now...Walgreen's sells both 100 and 800 speed film, so I can play...

Here are some FREE FREEWARE computer programs that will help you set exposure times.

You can find FREE exposure setting software here for both film and CCD! (http://users.rcn.com/assne/download.htm)

Michael Covington has written an excellent book, Astrophotography for the Amateur. Here's his astro-whatnot homepage, (http://www.covingtoninnovations.com/astromenu.html)
and here's his FREE software download page. (http://www.covingtoninnovations.com/astro/astrosoft.html)

I have both Couture and Covington's film programs, and have run them from a floppy on a WinXPPro machine. Just read the directions eight times on Couture's program of how to put your camera and scope setups in his program permanently (...instructions?...I don't need no stinking instructions...). Both programs will help you figure out how long to let the shutter stay open...and by the way, hit ebay and get a cable release!

PS Just downloaded Covington's little DOS program Almanac...spiffy, tiny (50kB!)! Yes, it ran under Win XP Pro. Not a bad little program to have hanging around...UTC, Julian and Sidereal dates, RA/DEC of Sun/Moon, rises/sets, and more...DOS still has its uses, folks...

Kaptain K
2003-Sep-10, 10:37 AM
The relationship is proportional, right? Find a good exposure time for 200, then double it for 100, or quadruple for 50?
As a first approximation, yes. The relationship is not quite linear for extremely long or short exposure times. This effect is known as reciprocity failure.

Pinemarten
2003-Sep-10, 01:03 PM
I am afraid to bring it up but........

Would 'push processing' be advantageous in telescope photography?
I remember it as loading 100ASA film then setting your camera to 200ASA.
Shutter speed, and aperture are then calibrated to 200ASA film. Your negs would normally come out dark.
Find a good photo-developer, ask him if he can 'push process'. If he sounds confused go elsewhere. If you start in the 'yellow book' on the phone , it will save legwork.
The grain is in the film. The higher the ASA, the lower the light, the more the grain.
If lower ASA film is under exposed, then 'over exposed' in developing, it will have better resolution (less grain) than higher ASA, but still capture the same image.

SarahMc
2003-Sep-10, 01:52 PM
I've had much better luck using a simple webcam modified to fit in a 1.25 diagonal or visual back. Film cameras at prime focus just don't cut it for planetary imaging. You could try afocal imaging with an eyepiece if you have an adapter, at least that gives you a higher magnification. My guess is that your images will be over exposed, and probably blurred/streaked from the mounts inability to hold the camera steady while the shutter releases. Images of Jupiter with my 8" f/10 SCT on film at prime focus produced a very small (maybe a 1/4") disk in the center of the frame. Detail was severly lacking - and that was with a cable release, mirror lockup, a very sturdy mount and short 1/125 sec exposures.

Baader IR material helps, or a regular glass IR filter if you have one. An adjustable polarizer is what I've used most of the late summer, as well as wratten filters for visual oberving of Mars.

With a web cam, you can make an AVI file of a couple minutes length, then use some of the stacking software like registax or K3CCD to stack up a couple hundred frames to bring out the detail. Works quite well, and no developing costs and/or waiting. Webcams are a lot lighter as well, so your mount doesn't suffer from the added weight of an SLR. You can also post process your images without having to go through getting a CD made by your photo store.