The Official Astronomy Thread

[SYN]

Doesnt seem like winter is the best time here in Cpt for this hobbie either.
How can one tell if seeing or transparency are good on a given night or morning without going through the whole mission of getting the scope out cooling it down and then only seeing that the air/sky isnt great.
It has now happened twice that i have got up at 05:00 only to find out about 30 mins later that conditions arnt that great. My guess was that still windless conditions would give good seeing and poor transparency, but this doesnt seem to be the case at all.

 

[Crusader]

It varies. Some nights you will have great seeing and bad transparency and vice versa.

One general rule of thumb is to look at how much stars twinkle. The more apparent the twinkling the worse seeing will be.

 

[SYN]

Does anyone know how big the difference is between a 8 inch and 12 inch telescope, when looking for detail in structure of galaxies, as well as resolution when observing planets?

 

[mercurial]

Does anyone know how big the difference is between a 8 inch and 12 inch telescope, when looking for detail in structure of galaxies, as well as resolution when observing planets?

I've had both telescopes and to be honest, I didn't see much difference. There is a difference, but it's not huge. But... in this case, bigger is better. Rather get the bigger scope.

 

[Crusader]

Does anyone know how big the difference is between a 8 inch and 12 inch telescope, when looking for detail in structure of galaxies, as well as resolution when observing planets?

There should be quite a bit of difference in brightness of the objects. For planets I don't think it will make all that much difference since you will have to deal with longer cooldown and seeing conditions would affect a larger scope more. To be honest I actually prefer the plantery views my 6" puts up. There's not as much glare on the planets as with the 10".

Galaxies, will still be faint fuzzies so don't expect a huge leap. With DSO obeserving there are loads of factors that come into play, the most import being how well you have trained yourself to see, light pollution and whether you have gotten fully dark adapted. I've read somewhere that to really start to "easily" see some detail on galaxies you need to view through an 18"+ telescope. And even then it's up to the observer how much they can tweak from the views and you won't get anything near to picture quality views.

 

[SYN]

Hi Guys. I am thinking of buying the following skyglow filter, hoping for better contract between sky and dso's especially galaxies and nebulae. -----> Baader Planetarium 2" Neodymium Filter http://eridanusoptics.com/store/index.php?main_page=product_info&products_id=560
Has anyone used one of these? Is does Baader make the best one (I see there are options available from Orion, GSO and Celestron too)? I is pretty unnerving spending a grand on a small piece of glass and not knowing if its going to improve viewing or not

 

[Crusader]

Skyglow filters in general have very little use and most people seem to be disappointed with how they perform.

A much better option would be to get something like an OIII filter or a Narrowband filter (UHC). These really do wonders on nebulae (emission nebulae in particular), but won't help on galaxies.

 

[mercurial]

In all honesty, all these filters don't do much, at least, that has been my experience. I paid well over R2k for high end filters and there ain't much difference compared to normal viewing without them. I'd rather use the money for high end eyepieces or to get a camera attached to the telescope (astrophotography).

 

[Crusader]

In all honesty, all these filters don't do much, at least, that has been my experience. I paid well over R2k for high end filters and there ain't much difference compared to normal viewing without them. I'd rather use the money for high end eyepieces or to get a camera attached to the telescope (astrophotography).

I have to disagree there. From my experience my OIII filter makes a huge difference when viewing nebulae. Orion doubles in size with faint tendrils and wisps easily visible. The Trifid goes from AV visible to very apparent. I'm more than happy with the performance.

Of course this will be highly dependent on the target and how dark your skies are. If you have a LP problem it won't perform miracles.

 

[Albereth]

Is there a system that you buy into that will grow? I understand that the main telescope part will be fixed to the mirror size. But could I add a tracking ssytem to the base? Could I add lenses? Could I add a camera? Etc.

 

[The_Pumpkin_King]

http://mybroadband.co.za/vb/showthread.php/251028-The-scale-of-the-cosmos

 

[Crusader]

Is there a system that you buy into that will grow? I understand that the main telescope part will be fixed to the mirror size. Bdedut could I add a tracking ssytem to the base? Could I add lenses? Could I add a camera? Etc.

It depends which direction you want to go and which type of scope. Most Dobs can't easily be upgraded for tracking without paying huge amounts. However there are tracking and even Go-to Sobs now available.

For visual tracking isn't that essential but nice to have. For photography you will need a needy EQ mount with worm gears for long exposures.

All telescopes will be able to use different eyepieces and most will allow camera attachment, but on a non tracking Altaz mount pictures will be limited to planets and the moon.

 

[SYN]

What will help on galaxies? Although the skies here in Table View arnt that bad, they are far from dark. I have looked at M83 (The Southern Pinwheel Galaxy) and seen all stars in the right place, confirming that I am indeed looking at the right spot and nudda. Same with Centaurus-A (Hamburger Galaxy) it should be there, but isnt. Should I rather leave galaxies all together and save hunting for them when I can get my scope out to a very dark sight? (which is VERY seldom)
I have managed to see M104 and the sculptor galaxy, but both are just just noticeable, as a VERY light smudge. I was hoping to darken to sky with a light pollution filter and so doing, make the contrast between to galaxy and background sky higher/better.....? I have never seen nebulae through a OIII or UHC filter, apparently the difference is amazing.

 

[Crusader]

Unfortunately the only things that helps on galaxies is aperture and more experienced eyes. You need to be fully dark-adapted and use every trick to tweak out some detail. They aren't called faint fuzzies for nothing.

Centaurus A was easy for me to see, and it does look like a hamburger with a dark band seemingly dividing it in two sections.

 

[Crusader]

Some of my observation notes can be seen at www.spacewallpapers.net/articles/observations.html

Centaurus A is at the bottom.

 

[Albereth]

It depends which direction you want to go and which type of scope. Most Dobs can't easily be upgraded for tracking without paying huge amounts. However there are tracking and even Go-to Sobs now available.

For visual tracking isn't that essential but nice to have. For photography you will need a needy EQ mount with worm gears for long exposures.

All telescopes will be able to use different eyepieces and most will allow camera attachment, but on a non tracking Altaz mount pictures will be limited to planets and the moon.

Thanks for the response.

The direction I would want to go is hobby. The girl child is keen on astronomy but wouldn't be spending too mnay late nights out in the cold . I would want to connect my Canon DSLR to the scope for some long exposures and that means tracking.

If there is a 'perfect' scope for me out of the box which one is it. and I do know that there are still some 'it depends' issues. Maybe a way of looking at it is that is there something that wouldn't disappoint - even if it isn't the ghee whiz best of the best?

 

[Crusader]

Thanks for the response.

The direction I would want to go is hobby. The girl child is keen on astronomy but wouldn't be spending too mnay late nights out in the cold . I would want to connect my Canon DSLR to the scope for some long exposures and that means tracking.

If there is a 'perfect' scope for me out of the box which one is it. and I do know that there are still some 'it depends' issues. Maybe a way of looking at it is that is there something that wouldn't disappoint - even if it isn't the ghee whiz best of the best?

Unfortunately astrophotography and visual observing is two different paths entirely. For photography your mount would be paramount. A 80mm APO refractory on a EQ5 Pro mount seems to be the minimum starting point. This is for widefield views. Visually it won't be much to write home about.

For visual you'd need the most aperture. Generally this means a Dob without tracking.

How much are you willing to spend?

 

[Albereth]

Unfortunately astrophotography and visual observing is two different paths entirely. For photography your mount would be paramount. A 80mm APO refractory on a EQ5 Pro mount seems to be the minimum starting point. This is for widefield views. Visually it won't be much to write home about.

For visual you'd need the most aperture. Generally this means a Dob without tracking.

How much are you willing to spend?

Basically, I hear you say that I should by a Dobsonian? See if I stick with it enough to drop the bucks to buy something with a decent mount? Although your Dob is about 3 times the cost of your refractor. And the dob should be easier for the family?

Trying to set a budget isn't something that I am good at. If I wants my precious I buy it. By the same token I don't like to waste money so I do as much research as possible.

I've seen the scopes on sale at some stores in Joburg. I don't touch because it'll mean fitting a large box in my car. When I'm ready I'll buy. I am not scared to bring stuff in from overseas either.

 

[Crusader]

I was posting via my cell so had to keep things brief, and unfortunately also slightly vague. So here's a more verbose reply.

My first suggestion would be to completely forget about photography when starting out. First get a decent knowledge of the skies, gain experience and do visual observing to see if the hobby sticks. Many beginners start out wanting to take Hubble-like images, but quickly give up on that and enjoy visual observing by itself. Even if you do go for astrophotography you will need a background on where the objects are located, how to set up the scope, best time/conditons for imaging etc and then astrophotography has a whole learning curve on it's own.

Imaging is not as easy as it seems to be. Unlike normal photography you'll need to know quite a bit more and have deep pockets to boot.

Unless you have a permanent observatory you'll be faced with this every night:
Set up the scope. Carry weighty mount outside, level the mount, add the OTA.
Provide power for the mount, your camera and most likely a laptop.
Allow scope to reach ambient temperature. (Can be between 30min to a couple hours depending on scope)
Do a very accurate polar alignment (for us in the SH this means going through the process of drift alignment).
Attach camera to scope. Get the correct focus.
Capture flat images. Capture dark images.
Point at target and start capturing images of object for 2 hours or so.
Pack everything away.
Do post-processing by stacking short exposures or tweaking long-exposures.

Equipmet needed:
Very good EQ mount with worm gears and port for auto-guider.
Imaging scope (the main OTA)
Guidescope (to add auto-guider to)
Camera (DSLR will work, but for serious use you need an actively cooled CCD camera)
Laptop
Power supply for scope, laptop etc.

Cost: Entry level type setup would run around: R35000- R40000 (EQ5 Pro Go-To Mount - R18000, 80mm ED Refractor - R10000, Auto-guider - R5000, Finderscope suitable for guidescope - R1500, misc accessories - R3000)

For visual use you can get away with a much lower budget. Depending if you want Go-To or tracking etc. A 8" Dob should set you back around R6000. Everything will have to be done manually but it's lots of aperture at a minuscule price. No extra accessories would be needed to start with. As you grow in the hobby you can add more eyepieces and other accessories as needed.

If you want tracking you can get a SW tracking Dob for around R14000, or wait and see if the Orion Go-To Dobs become available within the next year or two for a similar price.

A typical night out would be something like this:
Carry mount out. Put it on the ground.
Get the OTA and put it on mount.
Wait for the scope to reach ambient (a hour or so)
Put eyepiece in and view.

Basically, I hear you say that I should by a Dobsonian? See if I stick with it enough to drop the bucks to buy something with a decent mount? Although your Dob is about 3 times the cost of your refractor. And the dob should be easier for the family?

There really isn't an easy answer to this. For me a Dob was the best choice. The refractor was a cheapish experiment to see how I'd cope with refractors. It's pretty good on star clusters and decent on planets (does have quite a bit of purple fringe (CA) on them ), but for DSO's my Dob wins hands-down.

I find the refractor uncomfortable to use. The Dob is much more comfortable and pointing it is easier and I can the eyepiece stays at a height where I can easily sit and observe.

A Dobsonian is the cheapest entry point for the largest amount of aperture. It does have downsides though. You have to collimate it regularly and when viewing you have manually nudge it to track the object. For most that's no problem, but other people absolutely WANT tracking, which you can get - at a cost.

There are various factors which come into play for what would be right for you.
What do you want to look at?
How old is your child(ren)?
Do you have a problem with light pollution?
How much storage space do you have?
Are you comfortable with nudging the scope around?
Would collimation be a problem?
Are you willing to learn the sky?

Personally I'll take aperture over tracking and Go-To, but you might be different. An 8" Dob would be a great starter scope to test the waters.

If you are very serious (R20 000 worth of serious!) and want tracking. Something like the Celestron 8SE would be good. It's an excellent visual scope, has Go-To and tracking and later you can use the OTA on a EQ mount for photography.

 

[SYN]

I was pretty scared of the idea of grabbing a scope by the mouth and pulling it around before getting my 8 inch dob. I thought you would never be able to control the fine movements required for "manual" tracking at high magnification. But after having operated a dobsonian scope for a few months, nothing can be easier. I have effortlessly managed to track satellites with one hand while adjusting zoom and focus with the other. Hell i even managed to track a 747 the other day (at 48x magnification only ) It looked very weird seeing an upside down passenger airplane. My recommendation would be to buy a dob. And if you have more cash to spend than the R4k needed for a entry level dob., buy a bigger dob.