The Official Astronomy Thread

[Saalocin Rekked]

Finally finished reading through all the post, all 30 pages...

 

[Kalvaer]

What do you mean they are different on time? do you mean exposure time?

Yes, With digital you take tons of short exposure shots, and then stack them together, With film, you let the chemicals do their work with anything from 15min to a few hours depending on what your doing

assume that by adding more little weights I can have the main counterweight closer to the scope and therefore out of the motors way.

That might work. It all depends on where you are taking photo's for it to balance. If the weights are in a position that will not effect the motor for the duration of your shot. Then you can use the old ones

align the main axis toward geographic South(declination taken into account) then I set the same axis's inclination to the same as my current geographic latitude and that should technically give me perfect alignment? how would I check? I was thinking a small piece of paper with a hole in it just big enough for the object that I am viewing, so that I can see if it shifts.
Plus this specific telescopes tracking was said by one user not to track accurately longer than an hour.

Well you're limited to about 1 hour photo's then, But you can still get decent shots with that. Especially if your going planets and the like. DSO work best with big aperture anyway so it should not be a problem.

Now the way you have done it now, is a rough polar alighment, For astro-photography, You need to to be spot on. To get this right you need to zero everything on your scope and point it as close as possible to the SCP (Southern Celestral Pole). Its a region in the sky that is the "true south" that everything rotates around. In the Southern Hemisphere we use a star called Sigma Octantis to try and find it. You need to adjust your RA and DEC on your EQ mount so that when you are pointing at it. The entire sky will rotate around that point and never move, Even with your motor drives turned off.
Below is where it should be for somebody in JHB at about 7:45pm tonight

What is a illuminated eyepiece?
what is drift aligning?

An illuminated eyepiece is an EP with lights on the inside that look like cross hairs on a rifle scope. Drift alignment is when you use this EP to closely watch a star in the middle of these lines and you make adjustments to your RA and DEC based on how the star drifts in the FOV. Best website I know of to explain it is http://www.petesastrophotography.com/ (Click on the drift alignment section) The whole website is actually brillent for any astro photography

I myself being into photography(antique's, Film only) found it nearly impossible to get good film unless I was willing to fork out for a box, but haven't even bothered trying in the last few years. I would only be able to use standard Cafe' film at first whilst testing cant I take multiple exposures and stack them after scanning? whats the shortest exposure I need to take for stacking purposes?

There are a few places that still stock slide film in SA. I was able to find Fuji Provia 400 in one store, But had to import my Kodak Ektachrome E200. Also had the problem of having to buy a whole box, so its cheaper to import. Especially since a box will last you about 6 years if you take photo's every night for next 6 years.

I dont actually know of anyone that has stacked film. But that doesn't mean it cant be done. Its just that its much easier once setup to just take one long exposure shot in one go.

anyone know how to modify web cam for this type of imaging or maybe old B/W CCTV cameras?

Depends on the webcam. You can download a PDF I made some time ago on how to do it here http://www.wakesa.com/Temp/LogitechQuickcamPro4000Conversion.pdf

And this is a shot I took of Jupiter with it:

 

[Saalocin Rekked]

dang just lost another long post, damn Internet connection.

I do not understand why a good map and a compass cannot give me an exact polar alignment? geographic south and celestial south are the same also the height off of the horizon is also exactly that of ones exact latitude.

 

[mercurial]

Maybe type up your posts in Word or notepad and save it. Then just copy and paste so that you always have the info incase you lose your internet connection.

 

[marine1]

So being in the south pole you point south? I was pointing north and could never understand why things never worked well.

 

[Saalocin Rekked]

Maybe type up your posts in Word or notepad and save it. Then just copy and paste so that you always have the info in case you lose your Internet connection.

Thanks Mercurial, tiss advice I give but rarely follow. I normally type as you wont lose your text unless you actually submit it whilst Internet is down(which down here at the moment is every 20min) so I type it up and copy it to my clipboard Ctrl+C, which temporarily saves it in case. murphy's law every time I forget Internet is down

So being in the south pole you point south? I was pointing north and could never understand why things never worked well.

Marine 1, I am a noob so don't take everything I say. but yes we in the southern hemisphere have the south celestial pole. I roughly aligned my EQ1 mount south with a compass(not taking magnetic declination into account) and just used the Dial's on the main access to lift it to 30 degrees up which is my rough latitude in Durban and my tracking was spot on for visuals even with motor for up to 30min only thing I had to worry about is getting the tracking speed right as the Dial only has more or less option nothing more specific. I mention this has even in programs in stellarium(which I know might not be the most accurate) and books(whose article I'm frantically looking for) show that the celestial pole aligns with our geography.
But I'm waiting for Crusader to give us the low down on it.

Do you use a GO TO scope?
if so I have heard about a wonderful cheat for aligning them (warning 3rd hand info, I take no responsibility for any injuries occurring from elated running and jumping around LOL):

• 
  Put scope any where I guess pointing it south would be a good idea, select an object that you can find on your own, such as the moon.
  after the scope has tried finding it which it wont manage, manually move the scope to center on the moon.
  thereafter to keep it accurate manually center every other object.

 

[Saalocin Rekked]

Anyone know a guy by the name of Rodney Hyman he does realuminizing of mirrors?
Also I need to get my mirror(3") up to Jo'burg but cant really afford the courier fees; do any of you guys travel from Jo'burg to Durban frequently?

 

[Kalvaer]

I do not understand why a good map and a compass cannot give me an exact polar alignment? geographic south and celestial south are the same also the height off of the horizon is also exactly that of ones exact latitude.

They only can give you a rough alignment for two reasons.

#1: The maps we have are pretty accurate, but never as accurate as the stars.
#2: Unless you have a million dollar telescope, the chances that your settings are perfectly calibrated are pretty much zero. The smaller your EQ mount is as well, the smaller your RA and DEC controls are, and the bigger your margin for error. (Like with two triangles of simular interior angles but different interior area's)

For visuals, doing it like this is perfect. But for Astro-Photography, forget it. We all know (or will after this) that if you set your camera up on a tripod and take shots or various exposure settings, You'll notice that very quickly as the time increases, so does the length of your star trails.

With our camera's attached to our scopes, these star trails are now much longer for the same exposure because of the higher magnification. If your polar aligment is off by so much as 1/2 a degree, the things you are trying to image, will drift and cause "star trails". But you wont notice it visually... Unless your using an illuminated EP that is. I can setup my scope to track Saturn for at least 3 hours before it moves out the FOV... But I cant take photos like that because they blue

So being in the south pole you point south? I was pointing north and could never understand why things never worked well.

Tell me your joking and I'm being slow today.

 

[Saalocin Rekked]

Tell me your joking and I'm being slow today.

ha ha, dont be swak we all make mistakes.

ok so you saying it is possible but due to inferior equipment its not accurate enough... ok.
you mentioned that you could keep it in the illuminated eye piece for up to three hours, surely there is a quicker way to check your setup or else one would not get any pictures taken.

any alternatives to an illuminated EP?

 

[Crusader]

I don't use anything aside from my Dob and more recently the refractor on Alt-Az mount. That means that so far I haven't had to mess around with polar alignment, but also that I don't have astrophoto capability which is fine since I'm totally visual observer at the moment.

I do know that you need to align to the SCP and not the north (would you point it at the ground? ). For photography you need to be spot on and tracking needs to be very good - that's why I recommend visual above astrophotgraphy!

 

[Kalvaer]

I know we all make mistakes. But Marine has done some lovely astro work before aswell, so was wondering how he got that right if it was inverted

After a while you get used to setting things up pretty quickly for your standard location (ie: my backyard ) I usually do a drift alignment which takes about 15 min for RA and Dec each and I do these while my scope is cooling down. I have been lucky though and had everything seem spot on in 5 min even after moving locations.

As to other alternatives, just setting it up to the SCP. Its pretty easy to find.. if you can find Sigma Oct. (Which by the way, the Chairman of ASSA-JHB and I always joke around is a fictitious star invented by the americans to make us feel bad because of Polaris)

You do get polar alignment scopes as well which fit into EQ mounts, But you would have to check with the manufacturer if there is one for your mount

Remember as well it depends on what you are trying to take off. You dont need 3 hours to got brillent images. So you dont need to be as accurate. What people also do is use guiding scopes where they adjust the settings while taking a shot to get around small drift amounts.

This photo below was taken in 20 min, with a film camera by Pete from http://www.petesastrophotography.com/ and manually guided with a guide scope and motors

For photography you need to be spot on and tracking needs to be very good - that's why I recommend visual above astrophotgraphy!

I would to right now actually Its VERY time consuming. Only time I even try now is if I am out all night at a star party

 

[Crusader]

A trick Go-To scope owners use to center alignment stars is to defocus the star slightly (a Newt will show a donut) and then use that to make sure it's centered in the EP.

It might not be as accurate as a illuminated EP, but if you can keep a defocused star centered while tracking I think it should be pretty close.

 

[Saalocin Rekked]

As always thanks for the input guys; I have been trying to browse that website but its unfortunately under construction so will have to wait a while.
I suppose one could align it to the norther celestial pole only problem would be EQ mount cant go down but if it could, by dropping one tripod leg and actually rough aligning it you should still be able to track...

So if I have you correct crusader, if the defocused star is not exactly in the middle then of the EP it will be distorted some how?

 

[Kalvaer]

As always thanks for the input guys; I have been trying to browse that website but its unfortunately under construction so will have to wait a while.

Pete is a US ambassador, so he is all over the place. The important things though about drift alignment and his program to train are all working

 

[Saalocin Rekked]

You do get polar alignment scopes as well which fit into EQ mounts, But you would have to check with the manufacturer if there is one for your mount

Don'T forget that I don't even own a Telescope(besides for my 3" mirror in a tube with old murky .960 EPs) nor have any sort of budget for this, I ditched financial freedom to go back to school I'm practically unemployed; so I can only do things with the stuff I currently have available to me.

Even that sh1ty R200 12x60,no warranty and no collimation option binocs are uncollimated now it seems...
I do own an old pair of 10X40 binocs but still have to construct a rig to get them properly collimated. Studying is more demanding than working was I barely have anytime to do anything.

 

[Saalocin Rekked]

but also that I don't have astrophoto capability which is fine since I'm totally visual observer at the moment.

have you ever thought of an EQ base board for you dob? autotracks anysize dob for up to an hour and isnt very big few cm tall.
http://www.astronomy-mall.com/regular/products/eq_platforms/

 

[mercurial]

BTW, there is a new version of Stellarium out.

 

[Kalvaer]

BTW, there is a new version of Stellarium out.

Check the Pic I posted above Never had it installed on my Win7 machine so had to grab it last night to show the SCP.. Forgot to mention it though

 

[Saalocin Rekked]

I got version 10 beta, newer than that?
much prettier GUI but less stable, also much better location finder.

 

[mercurial]

Check the Pic I posted above Never had it installed on my Win7 machine so had to grab it last night to show the SCP.. Forgot to mention it though

Oh okay