[chupathingie]

OK, removing the hi-pass filter will in fact improve the HA sensitivity of your sensor by 2+ stops. Personally, I’d leave the sensor filterless if you have the option since the added IR sensitivity can be corrected in post for normal photography; at least you’ll be able to dual-purpose the camera. Even tho the atmosphere blocks a lot, digital cameras all come with an IR block to prevent them seeing through clothing (resulting from a lawsuit against Sony years ago, if I’ve not been misinformed). If you wish to capture HA only (which really is a big deal, allowing shooting even with a full moon), use an IR pass filter in the imaging train of the scope or screwed into the filter threads of your lens.

**important** Make sure that whoever does the mod replaces the IR block filter with a clear replacement of the same thickness and refractive index. This isn’t any help for astrophotography, but insures that your autofocus will still function correctly for terrestrial photography. Autofocus is calibrated for having a filter in place, and a naked sensor will result in very soft autofocus.

[chupathingie]

I refuse to fly until they do away with the TSA. Fark them.

bearsrepeating.gif

[chupathingie]

oh, Rav… have some astro-porn regarding the hyperstar: some guy showing off on an 8″.

[chupathingie]

There are a million things wrong with processing images in jpg… from enhancing artifacts when adjusting contrast to turning your histogram into a picket fence with even gentle levels/curves adjustments. 24 bit color is simply horrible for anything but a final image. Converting a 12/14/16 bit RAW file to native 48bit color gives you a file that you have to seriously abuse before you start chewing up your histogram.

[chupathingie]

heh… I’m just chock-full of nearly useless trivia that enables me to take truly mediocre works of photographic point-and-clickitude. 😉

[chupathingie]

I know orionid shoots both but he uses the .jpgs just as thumbnails that are easy for him to look at when determining what to process, and processes the .nef file.

I see I’m not needed here… That’s the ONLY reason I even bother shooting to .jpg.

[chupathingie]

Rav, flats need to be shot at 1/2 the ADU of your sensor; ie if you have a 12bit rig, the average value of your flats should be 2048 (8192 for a 14 bit). Deviating very far from that 1/2 value mark makes the flats worse than useless (they’ll degrade your images when applied). Therein lies my own problem with flats… I’m not at all sure how to go about retrieving that value. The whole concept of ADU is something you can spend a great deal of time on, and it dictates where your camera is most sensitive and produces the greatest contrast/dynamic range when you capture images. I have yet to find the time to tease all of the details out of the whole concept, but that aughtta get you moving with some search terms in the meanwhile.

As far as application of light flats goes, what I’ve found so far seems to indicate that your flats are normalized (centered and scaled around a value of 1…whether that’s a logarithmic scale or linear scale I don’t know yet). Your light subs are then divided by your master light flat to remove the vignetting and visible signs of any dust/yuckus that might be on your sensor.

Not sure what to say about the antennae galaxy… it looks like your focus was off, but I don’t know how dim the target is so that’s just a guess.

Oh and about those clouds… see below. At least I’m off on vacation for now.

[chupathingie]

no worries…I do a couple/three road trips a year so I’ll be throwing out invites for get-togethers off and on. Looks like we’re going to be heading more towards Arlington/Fort Worth for dinner anyhow… would love to hit that Brazil steakhouse out there, rave reviews all around for that place.

[chupathingie]

That f2 rig would certainly tempt me, but there are some decent deals on some new glass out there (Tamron’s 200-500mm f5.6-f6.3 comes to mind) or you could go the extender route to reach out a little farther with your existing glass… so far I’m impressed with my 2x, been shooting deer all morning with it mated to a 70-200mm f2.8L (jesus, that thing’s like toting around a piece of artillery).

re: Achromat/APO and camera lenses… Lenses have all those elements only partly for color correction, the rest of the reasons fall into field flattening and keeping those optical qualities up to snuff as the lens is zoomed in and out (if a zoom, of course). Telescopes usually are concerned only with color correction; with field flattening/coma correction being the next-in-line flaw that folks purchase add-ons for. A good scope designed for astrophotography use will already present a flat field and an image circle of at least 40-50mm. Field flattening is not much of an issue for long focal ratios…for instance your field is already pretty flat at the scope’s native f-ratio, and somewhat more curved with the FR in place; although my money’s on your FR having been designed to minimize field curvature out of the box.

[chupathingie]

*urp* 2 pounds of steak, sweet mashed potatoes and asparagus later (plus a pound and a half of Shiner…I didn’t have much room left for beer) and I’m about worthless LOL

Damn, saw this a bit too late. Hope you had a good time here in Dallas.

I’ll be back next weekend for Saturday evening on the return drive, but don’t know what’s planned for the evening yet… holler if you wanna trade a couple beers 🙂

[chupathingie]

It’s been strange… out where I live we expect tornadoes, but haven’t seen one in over a year. Go figger. Hope all y’all have a safe spot within running distance…be safe!

[chupathingie]

I have a 5DII, and can confirm that it has no on-board flash. The big thing I see in the MKIII over the MKII is 2 additional stops of ISO range, which is pretty impressive. The resolution is greater, but not by much. On-board HDR? that really depends on what it looks like… if it looks all HDR-ish, no thanks. If it’s done right and still looks real, then maybe.

[chupathingie]

Depending on the age of the mirror, the coat may be straight aluminum electroplate. Clean with a mild detergent and a minimum (preferably none) of physical abrasion. Don’t use any oxidizers, the film is thin and will suffer for it.

Plus side: if the coat is oxidized or otherwise damaged, it can be recoated, with aluminum plus high-transmission overcoats for less than the replacement cost of the mirror. If the mirror is hand-ground (which is likely given the plate on it) it may be of a higher quality than newer mass-produced mirrors. Sorry Meade/Celestron/Orion owners, Synta optics just don’t cut it. Hand-figured glass just can’t be beat in the parabolic primary arena, and this maker was proud enough to put his name on it… but still no guarantee until the light gets measured thru it.

Recoating can be done by most any company who does that, as the quality is dictated by the precision of the glass…just use a reputable coater.

[chupathingie]

Being a digital guy, but an admirer of film from way back in the day… I can’t say this is unexpected, but I consider it a loss to the art. I hope there will be niche hobbyists who provide substitutes for it…it’s gonna be pricey.

[chupathingie]

oh… diffraction spikes… love/hate here. They’re artifacts of the hardware, and I’m planning on curved vanes for my secondary mount. Yes, they’re pretty, to some of us, but they’re flaws in the imaging train… They’re a hallmark of the reflector/refractor war.

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