You should add back 1/3 of the filter thickness to your back focus. The change in index of refraction effectively shortens the path. Glass has an index of refraction of about 1.5. This means the effective distance is only (3/2)^-1 = 2/3 of the filter thickness. So if you have a 3mm filter, the optical path is only 2mm.
@Hidden.Light.Photography
2 күн бұрын
This is a very interesting, confusing and highly debated subject. This is how I’ve experienced this subject with my own equipment and have had great success. Now, this can be different for some depending on their equipment and how things are set up. From final mirror or lens to the focal plane is a specified distance as per manufacture. We need to align our camera sensor to the focal plane in order to focus. Yes, filters modify that by 1/3 of the glass thickness as glass has a different refraction rate than air. Let’s take 3mm since that’s the example you used. That means that our focal plane is now 1mm farther out so we need to move our camera sensor 1mm by means of draw tube. In the case of the coma corrector I use, skywatcher wants 55mm back focus from coma corrector flange to camera sensor on order for the entire field to be corrected. Adding a filter is affecting where the focal plane is located, however, the distance that I need to move my sensor is with the draw tube rather than spacers between the filter and camera sensor. In my personal experience with my equipment I see this when I switch filters and then I’m out of focus. I move my draw tube to refocus and still have a perfect field yet still get focus. If I space the camera sensor from the filter, I then have focus, but my field isn’t fully corrected because I changed the recommended distance from coma corrector flange to camera sensor. Again, this may be different for some with different equipment, however, let’s take Don Goldman into account where they measure from back of telescope to focal plane. One way I try to think about this is the light is essentially coned where the widest part is the final mirror or lens and the point is the focal plane. As you move your draw tube out, you are introducing the filter to a narrower part of the cone and moving in you are introducing the filter to a wider part of the cone.
@Skeptical-MCMXCIX
Ай бұрын
Loved the video. Thank You.
@Hidden.Light.Photography
Ай бұрын
Thank you, I’m glad you enjoyed it! Are you running a filter wheel currently or thinking about it?
@yervantparnagian5999
Ай бұрын
Another excellent video Tony.
@Hidden.Light.Photography
Ай бұрын
Thank you! How’s your project coming along?
@yervantparnagian5999
Ай бұрын
Which one? Lol. Working on separate stacks for Bodes and started Whirlpool.
@Hidden.Light.Photography
Ай бұрын
Both haha. Whirlpool is fun. I’m going to reimagine it this year
@physmc1
Ай бұрын
That video is gold and ZWO should probably reference it. I've noticed your tilt plate has some kind of o-ring, I don't remember seeing that in mine. Can you comment on what you are using? Assuming it is to mitigate light leak?
@Hidden.Light.Photography
Ай бұрын
Thank you, I appreciate that! If you’re referring to matte black ring on the tilt plate around 4:17 it’s a darkening ring for light leaks. This is a brand new camera as of a day prior to the video so it might be something ZWO implemented recently if you don’t see it on yours. The camera is an ASI2600MM Pro.
@physmc1
Ай бұрын
@@Hidden.Light.Photography Interesting, I don't remember mine coming with it. I guess ZWO reviewed the design as there were report of light leak at the tilter plate. Thanks for the follow-up info!
@Hidden.Light.Photography
Ай бұрын
You’re welcome! What camera do you have and how old is it?
@physmc1
Ай бұрын
@@Hidden.Light.Photography 2600mm pro and the 2600mc duo, both about a year old or so. Haven't tried to take out the tilt plate from the DUO yet, will check when I install the Photon Cage.
@Hidden.Light.Photography
Ай бұрын
Awesome! How do you like the duo? I was considering that one.
@jtepsr
Ай бұрын
Now I am a beginner and after seeing this, I have a ways to go before this step. I will stick with my zwo 2600mc pro for now but thanks.
@Hidden.Light.Photography
Ай бұрын
We all start somewhere, welcome to the hobby! I love the 2600mc. I was running that prior to the 2600mm and still run it. I have a whole series going over multiple pieces of equipment, workflows and processing. Let me know if you need help with anything :) What are you. Currently running for your setup?
@jtepsr
Ай бұрын
hi, i own all zwo equipment, am5, 2600mc pro, zwo 65 mm scope, asi air plus, zwo 30mm guide scope and 120 guide camera
@jtepsr
Ай бұрын
and yes i need help. my biggest problem is my weather conditions, i dont get enough shooting time
@Hidden.Light.Photography
Ай бұрын
That’s a very nice setup! How do you like it so far? Throw some stuff at me, let’s see what we can do! I hear you on the weather, it’s been very unusual lately. My best advice for this is plan ahead of time. In other words, if possible, have your sequence set up, framing etc. set up your equipment as early as possible so you can just jump right in and start imaging as soon as it gets dark. I run NINA so I am able to set up my framing, load it into the sequence, set up my sequence and save. From there, all I have to do is load the sequence and hit play. That saves a ton of time and really optimizes dark skies.
@jtepsr
Ай бұрын
Is there an email that I could use to ask you direct questions. I did something different when I got into this hobby, I was taught how to process the data first and now after getting the rig, I am learning the imaging part. I still get stuck at times, I need some tweaking
@MrMrduke1975
Ай бұрын
Love the skywatcher in the background! Is that a 6 or 8 inch?
@Hidden.Light.Photography
Ай бұрын
Thank you! It’s an 8”. What are you running?
@MrMrduke1975
Ай бұрын
@@Hidden.Light.Photography right now I’m just running a WO GT71 ZWO AM3, Asi533mc, ZWO 130mm mini guide cam and just bought a filter wheel, because once I start imaging sessions, I’m too lazy to get out of my pickup and change filters lol
@Hidden.Light.Photography
Ай бұрын
Very nice! I hear you there lol. I try to stay as automated as possible.
@OnceShy_TwiceBitten
Ай бұрын
SO no way to use OAG with all this? that is so lame, would nice to have a rotator as well.
@Hidden.Light.Photography
Ай бұрын
Yes and I agree, however, this is due to the 55mm of back focus required by the coma corrector. If I eliminated the coma corrector from the imaging train, I could run an OAG and all that would happen is my draw tube would be lower in order to line up with the focal plain. I have plans in the near future to go over OAG and demonstrate this.
@OnceShy_TwiceBitten
Ай бұрын
@@Hidden.Light.Photography Yeah but most people will want to run a coma corrector, reducer/flattener on their scopes etc. I mean not always, but not being able to and still have a rotator (or oag) I think the oag is better to have than the rotator, it's kind of lame is all, I DO Have a manual rotator I suppose since it's small, I can take the place of one of the spacers, and perhaps be lucky enough to get it all in with a reducer/flattener but I haven't tried yet, and that's not ideal. if anything, just to get the OAG out of the FOV, and not much more lol. Unless I want to go out and rotate for each object, which defeats the purpose of all the other automation haha.
@Hidden.Light.Photography
Ай бұрын
I agree 100%, it can be very annoying. I was trying very hard to find rotators and filter wheels that are thin enough to be able to include OAG.
@JeffL81
Ай бұрын
don't over tighten the screws he said so countless times
@Hidden.Light.Photography
Ай бұрын
Yes lol. Better to remind a lot than risk damaging expensive equipment. A reminder for both everyone watching and me.
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