8 inch collapsible dob accessories

Exclaymation (Gustavo) · #1 21-11-2012, 12:31 PM

Hey guys,

I have been watching this forum for a bit now but never asked anything, so this is my first post.

As the title says, I have a Saxon 8 inch collapsible dobsonian telescope and I have had it for about 8 months now. It doesn't have a go-to mount because I couldn't afford it and I also wanted to learn where objects were by my own merits. I have become pretty good at it and can control it pretty well. So I have just been looking around for some motorized go-to bases, but I haven't really had much luck. Any suggestions for a good strong and steady base? I would like to get into astrophotography and my SLR is really small (smaller than those NEX cameras) and light, so it wouldn't add much weight to the scope. Price is a bit of an issue for me, so the cheapest the better. Any suggestions?

I also read that perhaps dobs are not the best for astrophotograpy, if so, what would be a good scope?

I got given a 4mm lens from a friend that work in Australian Geographic, but I never really liked it. I don't know if it is a dodgy lens or what, but I find that it doesn't add much to my experience. Could anyone suggest some lenses that would go well with it? I have the 2 stock lenses (20 and 10mm) and a barlow (which I don't really like it). Any suggestions would be welcome.

Also, the scope is collapsible and I don't have one of those blankets that people wrap the scope on to reduce light, is that a good investment?

Thanks guys and I apologize for the long post.

Skieswatcher (Mustafa) · #2 21-11-2012, 01:14 PM

Hi, after going through the drama of choosing what scope to buy, I chose an 8'' solid tube dob knowing that in the future it could be mounted onto an eq for AP. It seems that a collapsible dob is not ideal for AP because its Alt/Az mounted and even with the goto, the tracking wouldnt be accurate enough.
There's always the option of a tracking platform, which is quite pricey unless you're able to make one yourself.

Exclaymation (Gustavo) · #3 21-11-2012, 04:17 PM

Yeah, those bases seem to be fairly expensive. I found a dyi kit for about $239 plus delivery (which should be a fair bit) but I have to cut the wood. Seems like a good idea, although it is only uni-axial. So the collapsible scope is not too good for go-to? would really like to get a go-to, but just tracking is good enough. I guess I will keep looking and perhaps I might get that base. Thanks for the reply.

barx1963 (Malcolm) · #4 21-11-2012, 05:30 PM

Gustavo
Firstly that wasn't a long post!
As regards your question there are a few issues to cover. You will find that visual and imaging have very different requirements and dobs are usually quite limited for imaging use. Thay can be used for targets that require short exposue which would be the brighter targets eg moon, planets and sun (with appropriate filters!!!). Usually it is not possible to attach a camera as the focal point is inside the focus tube so the primary mirror has to be moved up the tube. You can do afocal which means holding a camera up to the eyepiece and using autofocus to focus and snap away. Takes a little practice and works best on the moon.
For deep sky stuff you need to mount on an EQ mount that can take guiding. Platforms for dobs can work but are not capable of being guided.
Guiding BTW is different to tracking, tracking means a scope is turning with the sky, guiding means you use an autoguider to correct any small errors in the tracking and allows much longer exposures.
The problem you may have is that a collapsible scope is not designed to be mounted on an EQ mount, so may need to handyman work to get it going.

Malcolm

Exclaymation (Gustavo) · #5 21-11-2012, 06:26 PM

Thanks for the reply Malcom. So the tracking bases are not ideal... I wasn't aware of that. Yeah, it seems that the collapsible dob ain't really meant to be used for ap. That is a bummer.

What about some accessories which boost my experience, such as lenses, covers, etc. Any suggestions?

GraemeT (Graeme) · #6 21-11-2012, 07:41 PM

G'day Gustavo,
Yes, generally tracking platforms are not ideal for long exposures. HOWEVER..., I have an 8" collapsible dob for which I built an equatorial platform and then later purchased a Skywatcher goto dob mount. The EQ platform worked very well for visual use, holding DSOs in the centre of the field for up to an hour. Likewise, the goto mount seems to be just as accurate without the need to reset the base at the end of its travel. The problem with imaging with a tracking AZ mount is the rotation of the image field that doesn't occur with an equatorial (GEM) mount, and which prevents you from stacking the images. I was advised very early in the piece, that if you want to get involved with imaging, be prepared to spend lots of money, don't expect to do it on the cheap!
That said, I can get quite reasonable planetary pics with my webcam.

wavelandscott (Scott) · #7 22-11-2012, 02:14 AM

For an 8 inch Donsonian mounted reflecting telescope used visually, I often recommend a good sturdy adjustable height chair.

The addition of the adjustable height chair improved my visual experience and enjoyment a great deal. I've found that viewing in comfort has enhanced my ability to see detail and allowed me to observe for longer periods of time.

Build your own or buy commercially a sturdy adjustable height chair is a great addition to your astronomy tools.

ZeroID (Brent) · #8 22-11-2012, 09:30 AM

The Moon is still doable with a DOB. My exposures with the DSLR are only 1/300 sec and you can also do the webcam\avi stack process in short bursts. Planets possibly as well with webcam. Yes it is not ideal but as a starter it gives you experience and some tangible reults.

I'd suggest finding a way to mount and align your small camera to the focusser and taking some a focal moon pics to begin with. You can buy brackets etc for this from Bintel and other suppliers. It will get you going, frustrate the heck out of you and whet your appetite for more. The moon is quite fascinating in closeup and you will learn HEAPS about processing and the challenges in astrophotography.

We expect to see results posted here ...

Exclaymation (Gustavo) · #9 22-11-2012, 10:41 AM

Yeah, I am aware that I will have to spend some cash for me to have a respectable tracking base. I am looking around for bases built by for Saxxon scopes and perhaps I might be lucky and find one.

I have this chair I use with my scope that is the perfect size. I agree that a comfortable position can certainly make the experience better. I also have a stand that I put the dob on sometimes for when I feel like standing up.

Exclaymation (Gustavo) · #10 22-11-2012, 10:45 AM

Quote:

Originally Posted by ZeroID

We expect to see results posted here ...

Yeah, that is a pretty good idea. I will start looking for a mount straight away. I made a home made mount for my phone (that's what I was using before I got the SLR) and took a couple of photos last night.
But I accept your challenge. In the next few weeks, expect a slew of moon and with a bit of luck, planet pictures from me.

rustigsmed (Russell) · #11 22-11-2012, 10:47 AM

Hi Gustavo
I have a skywatcher dob with goto tracking.
If you want to see what a dob can do in terms of astrophotography check out my pics. I didn't have to move my mirror at all, not sure about yours.

Best of luck

Rusty
http://www.flickr.com/photos/80336656@N07/

Exclaymation (Gustavo) · #12 22-11-2012, 11:08 AM

Hi Russel,

wow... those photos are amazing! On the description of the photos, you have details such "35 x 20sec subs". Does that mean that you took 35 photos with 20 seconds exposure each? And what does the subs mean?

I NEED at goto base now....

rustigsmed (Russell) · #13 22-11-2012, 11:25 AM

Quote:

Originally Posted by Exclaymation

Hi Russel,

wow... those photos are amazing! On the description of the photos, you have details such "35 x 20sec subs". Does that mean that you took 35 photos with 20 seconds exposure each? And what does the subs mean?

I NEED at goto base now....

Thanks for the kind words.

In short yes it is 35 shots of the same object with each photo being a 20 second exposure. 20-25 seconds is really the maximum exposure time then it starts blurring the image too much.

It's all about stacking images to reduce noise in the image and you can bring more detail out. I use a free program called deep sky stacker.

For planets it's different, a video is usually taken and another program registax 6 does aligninging of the frames and stacking of the image.

You will need a camera capable of high iso otherwise the objects will be too dark.

So capturing the information is a small part of it, processing the data in these programs and photoshop is perhaps a bigger part of it.