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How to measure moons distance from target.

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#1 Krawbeard

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Posted 20 August 2018 - 12:49 PM

I'm imaging narrowband in my backyard and was curious how one goes about measuring the distance of your target to the moon in degrees.

I've mostly just went by guessing for now which is if the moon is full dont image anything unless its halpha and it's a good distance away. Sulfur ii isnt bad when the moon is less and further away but for oiii just dont even bother with the moon unless you're at dark skies and the moon is either setting or small crescent.

But I've been reading on the forums here that say if your target is 120degrees from the moon then you have a probable chance of lrbgoiii images and 60degrees for haS.

So as silly as it sounds of me to not know this. How does one properly do so? I have sky safari and stellarium. Just looking to see anyones logical input that can help me before I start shooting a bunch of oiii frames when I could be getting ha and sii the whole night.

What can I say, I'm an opportunist and if the light is green I'll go.

Clear skies

#2 Alex McConahay

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Posted 20 August 2018 - 01:44 PM

You do realize that these are just gross rules of thumb......And whether your skies are clear, have moisture in them, air pollutants, what your targets are, and a whole lot of other things mess with the generalizations. 

 

Having said that, most planetarium programs will tell you how far one object is from another. My Sky Safari for instance lets me search for one object, and then another, The data for the second tells me how far I am from the first. 

 

Of course, a planetarium program/sky chart will tell you. 

 

And, then there is the simple rule, that lets you use your fingers/hands as a guide as to how far two objects are apart from each other:

 

 http://c.tadst.com/g...with-hand.png?1

 

Alex


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#3 ks__observer

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Posted 20 August 2018 - 02:11 PM

Those really should be taken as rules of thumb.

I have shot Ha objects about 30 or 40 deg from a 50% Moon and got good data.

Clear skies are often hard to come by. 

Of course dark skies are best. 

But take advantage of what you have and make the best of what you have.

If you only wait for all the stars to align (half pun) you might be waiting a long time and you might miss out on getting experience and getting some great shots, and having fun.

Experiment, experiment, experiment ….

 

Astroplanner is a great tool that gives lots of useful info including distance to Moon:

http://www.astroplanner.net/


Edited by ks__observer, 20 August 2018 - 02:32 PM.


#4 Krawbeard

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Posted 20 August 2018 - 02:30 PM

Thank you 2 for your replies. I did the sky safari trick and it worked. And thanks for the reminder on the sky quality. I try to be kinda picky on seeing and especially anything resembling haze in the skies especially if I'm shooting at a higher focal length. And if transparency is garbage I just kick back and enjoy some coffee or time out away from the house.

I'll be sure to experiment and see how the results look. Perhaps I'll do some comparisons and see how much contrast is brought out or washed out. After all it's the fun of discovery

Clear skies

#5 denny-o

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Posted 20 August 2018 - 02:59 PM

I was going to comment that a moon width is a half degree and you can use your fingers to see how many moons to your target, then I noticed you are in Texas and everything is bigger in Texas, so I guess that won't work wink.gif



#6 CharlesW

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Posted 20 August 2018 - 03:03 PM

CCD Navigator would be your friend here. It will tell what you what targets are available and for how long, based on the time of year. It will tell you what filters are safe to use, during what hours of the night, based where the moon is. If you capture through CCDAP it will also track the number of exposures you’ve taken, with which filter, and set up the next imaging run with that in mind. It would be the best $150 you’ve spent. 



#7 Krawbeard

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Posted 20 August 2018 - 03:28 PM

Interesting, I'll have to give that a go. Lol I just bought an autofocuser so itll be a while before I take another trip down the rabbit hole.

Hahaha yeah we use cows to measure degrees here in Texas and I can't afford a crane right now


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