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#1 Trucker360

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Posted 03 March 2021 - 02:59 PM

last night i took the canon 450d out, with my new button thingy i cant spell the actual name of, with the new to me 75-300mm lens. oh and regular tripod and took these. and well, it raised some more questions.
 
so to start, we have the fore mentioned equipment. I'm waiting to get my adventures in astrophotograpy bundle from Orion. they was back ordered until 3/23/21. (thanks covid) So i decided to take this time to practice with what i have, which is what raised the questions.
1) what am i doing wrong on focusing?
2) how do i know what size bat mask i need?
3) why is 1600 ISO terrible at 30 sec or longer pics, but not at say 20?
4) if i get hot and heavy into this, wouldn't 1600 ISO suck for 2 min exposures?
5) i think i need a sun shield because of all the unwanted streetlight pollution. its not feasible for me to venture out of town every night. or every good night.....
6)b i have stellarium, and starwalk 2. one or both don't show nebula and the such. any other good things for that.(i really need some books, but just bought a home, and have lots of renovations to do.)


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#2 Trucker360

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Posted 03 March 2021 - 03:01 PM

Still on not one piece of tech does it all. Lol. Here's the pics. 75d548370cfd5a89bba3bf4bfcc4ab11.jpg5931a50540ef26f625a129ef1d435d49.jpg4f5cab7ad3bc460c9dcfd924417fd5df.jpg516e9d8a16ce1e410086445fa72e7451.jpg

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#3 photoracer18

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Posted 03 March 2021 - 03:12 PM

If your "mount" is just a photo tripod you need to make your frames a lot shorter. With a non-tracking mount the length of exposure you can do without star trails is a function of the magnification on the lens you are using. The longer the lens the shorter the exposure. You should be playing more in the 20-30 second range if near the max zooming of the lens. As for a Bahtinov mask you want to get something that is the size of your sunshade/dewshield. They usually have some adjustment for mounting. You will need to stack multiple frames so look at getting some freeware like Registax to stack individual frames. This allows you to toss away bad frames also.


Edited by photoracer18, 03 March 2021 - 03:13 PM.


#4 rblackadar

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Posted 03 March 2021 - 03:14 PM

Regarding ISO, leave it at 1600. That's probably the best setting!

 

Your biggest issue is lack of tracking, that's why you have star trails. Try shooting at 75mm and 1sec exposure, take lots of frames and stack them in Deep Sky Stacker. Don't shoot longer than a couple seconds until you get a star tracker of some kind (there are some pretty cheap options).

 

As for focusing, yes there are masks, but the easiest thing to do is point to a bright star (like the one in the photo) and go into Live View. (You must briefly set the shutter to something long like 30sec, to make the star appear in Live View.) Push the zoom button to 10x and focus so that the star diameter is smallest. Then re-set the shutter speed to what you want for the photo.

 

Stellarium is great for nebulae, I don't know what your issue is. Use the PgUp key to zoom in, it could be that they are not showing up at the scale you're looking at.

 

EDIT -- depending on how fast your lens is, it may be hard to see stars in Live View. If you can't, you have to take test photos, changing the focus until it's right. Masks can help with that, but I'd say don't bother with one until you get more experience.

Also, make sure you snoot in RAW. Orion nebula is a good target for you to start on.


Edited by rblackadar, 03 March 2021 - 03:26 PM.

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#5 jonnybravo0311

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Posted 03 March 2021 - 03:17 PM

Button thingy is good enough smile.gif

 

OK... so, it isn't the ISO that is terrible at 30 seconds. It's the fact that we're on a spinning planet hurtling through space. What you are seeing is the effect of that spin. That's exactly what the trackers like the Star Adventurer counteract.

 

There's a very general rule of thumb for how long you can expose a picture before noticing the trailing of the stars. It's called the 500 rule. How it works is you take the number 500 and divide it by the focal length of your lens times any so-called "crop factor". The resulting number is about how long you can keep that shutter open (using the button thingy).

 

Let's show you some numbers, using your own camera (which is an APS-C Canon sensor with a "crop factor" of 1.6) and lens. I'll assume you shot at 200mm - which is about halfway for your lens:

500 / (200 * 1.6) = 1.56 seconds

Therefore, your MAXIMUM exposure time to avoid star trails with your camera and lens at 200mm is 1.5 seconds. You took exposures of 30 seconds... which is 20x longer. Therefore, you see the trailing effect.


Edited by jonnybravo0311, 03 March 2021 - 03:18 PM.

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#6 Trucker360

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Posted 03 March 2021 - 07:01 PM

If your "mount" is just a photo tripod you need to make your frames a lot shorter. With a non-tracking mount the length of exposure you can do without star trails is a function of the magnification on the lens you are using. The longer the lens the shorter the exposure. You should be playing more in the 20-30 second range if near the max zooming of the lens. As for a Bahtinov mask you want to get something that is the size of your sunshade/dewshield. They usually have some adjustment for mounting. You will need to stack multiple frames so look at getting some freeware like Registax to stack individual frames. This allows you to toss away bad frames also.

should i have a dew shiel/sun shade. if so, how do i know what size to get? same goes for the mask. i guess i didnt word it correctly



#7 Trucker360

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Posted 03 March 2021 - 07:06 PM

Regarding ISO, leave it at 1600. That's probably the best setting!

 

Your biggest issue is lack of tracking, that's why you have star trails. Try shooting at 75mm and 1sec exposure, take lots of frames and stack them in Deep Sky Stacker. Don't shoot longer than a couple seconds until you get a star tracker of some kind (there are some pretty cheap options).

 

As for focusing, yes there are masks, but the easiest thing to do is point to a bright star (like the one in the photo) and go into Live View. (You must briefly set the shutter to something long like 30sec, to make the star appear in Live View.) Push the zoom button to 10x and focus so that the star diameter is smallest. Then re-set the shutter speed to what you want for the photo.

 

Stellarium is great for nebulae, I don't know what your issue is. Use the PgUp key to zoom in, it could be that they are not showing up at the scale you're looking at.

 

EDIT -- depending on how fast your lens is, it may be hard to see stars in Live View. If you can't, you have to take test photos, changing the focus until it's right. Masks can help with that, but I'd say don't bother with one until you get more experience.

Also, make sure you snoot in RAW. Orion nebula is a good target for you to start on.

i ststaed i have lack of tracking. thats not the problem. the problem (pics not posted for reference and deleted) is that at 1600 at any focal length with a 30 sec exposure, the pics are very bright and orange ish. same setting but a 10-20 sec exposure, and you get whats pictured. which to me indicates too high a iso, or street light pollution. so, in my eyes, sun shade type thing or lower iso to fix the orange, bright problem.



#8 Trucker360

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Posted 03 March 2021 - 07:11 PM

Button thingy is good enough smile.gif

 

OK... so, it isn't the ISO that is terrible at 30 seconds. It's the fact that we're on a spinning planet hurtling through space. What you are seeing is the effect of that spin. That's exactly what the trackers like the Star Adventurer counteract.

 

There's a very general rule of thumb for how long you can expose a picture before noticing the trailing of the stars. It's called the 500 rule. How it works is you take the number 500 and divide it by the focal length of your lens times any so-called "crop factor". The resulting number is about how long you can keep that shutter open (using the button thingy).

 

Let's show you some numbers, using your own camera (which is an APS-C Canon sensor with a "crop factor" of 1.6) and lens. I'll assume you shot at 200mm - which is about halfway for your lens:

500 / (200 * 1.6) = 1.56 seconds

Therefore, your MAXIMUM exposure time to avoid star trails with your camera and lens at 200mm is 1.5 seconds. You took exposures of 30 seconds... which is 20x longer. Therefore, you see the trailing effect.

correct. this is the lets screw everything up phase.

i have a tracker coming, but tails isnt my big concer. in the previous reply i talk about the orange coloration of 30 sec vs black of 20 sec. which is either light pollution or exposure. so, lets add a mouth to the equasion. is the orange the reasons i listed?



#9 Stelios

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Posted 03 March 2021 - 07:57 PM

The best ISO for Canon is 800 or 1600 (no lower due to read noise). 

Bahtinov mask should match the size of the objective lens (or star end of camera lens). That's where it goes. Most of them are adjustable. The central part is what you really care about. 

 

There should be no color difference because of exposure length, other than obviously brighter images (and longer trails). So anything you have is due to some light creeping in. 

No idea on available dew shields for a 75-300mm lens. If none exist, then similar to the Bahtinov mask situation, you need to measure the diameter of the large part of the lens, and look for a flexible dew shield with velcro fastening of the approximage dimensions you need.



#10 Trucker360

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Posted 03 March 2021 - 09:03 PM

Here's tonight's images. 300mm (for fun) got focus! 5sec exposure, but still trails. But, again, this was for fun.
Also, I experimented. The overly orange color at higher exposure was street lights. I got a sun shade or dew shield thing. Now to find some vanta black to cut any light from bouncing around in there. Lol. Think 7 sisters was a little out of focus, and about 2-300mm maybe less. Don't remember. 2ebfce8a399271517693e544ae6b040d.jpg9e121abfcf74f6cf7166c9145f10545d.jpgf27a4f718b68eb091f45071a6486cc9b.jpg

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#11 Sam Danigelis

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Posted 04 March 2021 - 03:52 AM

See? Big improvement in only a day! Now, what Johnny said, cut it down to 2-second exposures ("subs"), and you could have some nice, sharp stars. Then just stack a couple hundred together. Shoot, at 2 seconds you could take 400 subs pretty quickly. You've got an intervalometer, right?

#12 Trucker360

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Posted 04 March 2021 - 05:36 AM

See? Big improvement in only a day! Now, what Johnny said, cut it down to 2-second exposures ("subs"), and you could have some nice, sharp stars. Then just stack a couple hundred together. Shoot, at 2 seconds you could take 400 subs pretty quickly. You've got an intervalometer, right?

Yes I have one. That's "the button thingy" lol

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#13 BobE102330

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Posted 04 March 2021 - 08:30 AM

As for nebulae missing in Stellarium, click on the DSO button (looks like a spiral galaxy) on the bottom toolbar to enable them. Always available in search, although sometimes popular names aren’t found. 


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#14 Trucker360

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Posted 04 March 2021 - 09:39 AM

As for nebulae missing in Stellarium, click on the DSO button (looks like a spiral galaxy) on the bottom toolbar to enable them. Always available in search, although sometimes popular names aren’t found.

I messed with it last night. Kinda. I need more play time with it.

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