DIY Light Box

I'd like to share the pictorial steps about how I went about building this but I also want to be sure I'm following forum rules for posting multiple images. Something about a picture being worth a thousand words, blah, blah, blah...

From the forum rules regarding posting more than 2 images: "you may exceed above photo sharing limits, but only if discussion requires it (e.g. lens test examples, more problem example photos, competitions)."

I am only concerned because I believe I will have to insert these 9 (linked) images across more than one post. I'm not trying to create a personal gallery, just showing how this was done. So hopefully this is within the guidelines. If not, please delete the thread. (Don't ban me mods! I'm begging you!!!)

So anyway... I've learned that in addition to the image files, darks and bias images, I need to take flats too if I want to process my deep sky images to be the best they can be. The one part that was frustrating was shooting flats - assuming I don't stay out until the sun comes up. Therefore, I decided to hack together a light box to take the flats. I started with a few 24" x 36" foam core boards that I've had lying around for a while for some unknown reason. One nice thing about these boards was that they had a self-adhesive side on one side. I used this to stick aluminum foil to certain parts, and to aid in the rigidity of the overall box by doubling the thickness. I got most of the parts from Amazon (details below).

Here's how it went:

IMAGE LINK: http://s177.photobucke​t.com …20Forum/IMG_237​6.jpg.html

IMAGE LINK: http://s177.photobucke​t.com …20Forum/IMG_237​7.jpg.html

IMAGE LINK: http://s177.photobucke​t.com …20Forum/IMG_237​5.jpg.html

There seems to be a problem with these three. I didn't think there was a size limit if they were linked.
http://s177.photobucke​t.com …20Forum/IMG_237​8.jpg.html

http://s177.photobucke​t.com …20Forum/IMG_238​9.jpg.html

http://s177.photobucke​t.com …20Forum/IMG_238​8.jpg.html

IMAGE LINK: http://s177.photobucke​t.com …20Forum/IMG_240​3.jpg.html

IMAGE LINK: http://s177.photobucke​t.com …20Forum/IMG_239​8.jpg.html

IMAGE LINK: http://s177.photobucke​t.com …20Forum/IMG_240​1.jpg.html

In answer to your question:
In the "Share" areas IMAGE POSTING RULES specifically state under "Allowed # of images:"
We allow 2 attachments by the OP per thread, OR 8 embedded (linked) images, OR a combination of 2 attachments + 6 embedded (linked) images, totaling 8 per thread.
(Maximum 1280 pixels on any side.) You can always just post a link to more, though, or better yet, post a link to a gallery so we don't have to click on each image link.
Some exceptions are group threads, like "Show Me...", "Post your best...", equipment reviews, Tutorials, etc.
You may add a few additional photos if requested, but only in a reply to other member's post and request.

Phil Light wrote in post #18005811
So anyway... I've learned that in addition to the image files, darks and bias images, I need to take flats too if I want to process my deep sky images to be the best they can be. The one part that was frustrating was shooting flats - assuming I don't stay out until the sun comes up. Therefore, I decided to hack together a light box to take the flats.

can you tell me what the heck a flat is?

actually, it like to know what the darks and bias images are too. A link or a few more key words to search would be fine if you don't want to get into the whole thing.

Left Handed Brisket wrote in post #18005877
can you tell me what the heck a flat is?

actually, it like to know what the darks and bias images are too. A link or a few more key words to search would be fine if you don't want to get into the whole thing.

Given that I'm extremely new at celestial imaging, I'll do my best. There are several people on this forum who can probably explain it much better than I can.

When you shoot extremely faint, deep sky objects, you frequently have to take 20 or more images to be combined (stacked) later, with each exposure lasting anywhere from 20 - 30 seconds to 20 - 30 minutes. Long exposures like this will greatly accentuate any noise, vignetting, sensor dust and other issues like these. So your image files of these faint objects usually won't look very good straight out of the camera. To compensate for this, software programs like Deep Sky Stacker (DSS) have been written that utilize additional images you need to take. Then, when stacking the images, it utilizes all of the lights, darks, flats and bias images to produce an image that separates the signal (stars) from the noise (noise) . You should probably shoot about as many darks, flats and bias images as you did for each exposure setting you used to shoot your lights.

Over-simplified explanation:

Lights
The "lights" are your image files. They contain the "signal."

Darks
The darks are files that you shoot with the lens cap on, but with the same settings you shot the lights, i.e., same iso, same exposure length, same ambient temperature, etc. These will most likely contain the long-exposure, iso noise that you don't want in your final image.
The "darks" are the files that DSS (for example) uses to calculate the long exposure noise and remove it from the output image.

Flats
The flats are images that you preferably also shoot at the same time as your "lights." However, these are shot with a light source (usually a blank spot in the daytime sky, or stretching a white t-shirt over the front of the telescope and pointing a light source at it. The flats should be shot using aperture priority so you've got basically a well exposed, blank image. An image taken like this will accentuate vignetting and sensor dust.
Flats help DSS identify and eliminate that vignetting and the dust spots on the sensor.

Bias
Bias images can be shot at the same time as your lights or not. These images are shot with the lens cap on, using the fastest exposure setting available to your camera. You need bias images that were shot with the same iso you used when you shot your lights.
My understanding is that bias images serve a similar purpose as darks, that is to eliminate noise from the final image. I'm sure someone with more knowledge can update or correct any of this information.

(Side note, I find it interesting that it was only a month or so ago that I was asking this same question.)

PhotosGuy wrote in post #18005865
In answer to your question:
In the "Share" areas IMAGE POSTING RULES specifically state under "Allowed # of images:"
We allow 2 attachments by the OP per thread, OR 8 embedded (linked) images, OR a combination of 2 attachments + 6 embedded (linked) images, totaling 8 per thread.
(Maximum 1280 pixels on any side.) You can always just post a link to more, though, or better yet, post a link to a gallery so we don't have to click on each image link.
Some exceptions are group threads, like "Show Me...", "Post your best...", equipment reviews, Tutorials, etc.
You may add a few additional photos if requested, but only in a reply to other member's post and request.

Hi Frank, and thank you for the clarification. I only brought it up because this post is far more of a tutorial on how to do something, rather than my usual, "Hey! what do you think of my photo pictures? It seemed a LOT easier to explain how I did this using a series of pictures rather than a couple of pictures and a ton of jibber jabber. I like to think of myself as the "IKEA" of DIY instruction.

Phil Light wrote in post #18006002
Hi Frank, and thank you for the clarification. I only brought it up because this post is far more of a tutorial on how to do something, rather than my usual, "Hey! what do you think of my photo pictures? It seemed a LOT easier to explain how I did this using a series of pictures rather than a couple of pictures and a ton of jibber jabber. I like to think of myself as the "IKEA" of DIY instruction.

No problem. You're good in this thread.

Thank you for the explanation. It sounds like that process could even be important for wide angle night shots?

I really want to buy a telescope that can be adapted to my camera, but it is pretty low on the list of things that need to be taken care of around here. My kids are about at the right age for getting into it too.