View Full Version here: : A little help
06-04-2012, 06:51 PM
hello everyone. just need a little help. i have a 10" truss dob but still only have the two standard eye pieces and a 2x barlow. i want a decent view of mars or saturn but only get small hard to see images. can anyone advise me of some eye peices that will be good to use for planetary objects? some decent combinations prehaps and what i can expect to see.
06-04-2012, 09:59 PM
I'm not sure what the standard eps are that come with your scope. Magnification for viewing planets or anything through a ground based scope is limited to about 250-300x on most nights. If you've got an ep of about 10mm fl and a 2x barlow you will be at about 240x assuming the fl of the scope is 1200mm. So this would be about as good as you'd get except on nights of exceptional seeing. Even then on most nights i find planets are best viewed at about 180X as although the mag goes up the image quality goes down. Especially if you are viewing when the planet is low in the sky and you're looking through lots of unstable air. You won't get much joy out of Saturn till 3 am at present. You may see some faint bands, but mostly what will stand out are the rings. Mars you should be able to see good detail on a small disc with patient observing. It won't jump out at you, but you should still see ice cap and dark features.
Hopefully your scope is well collimated otherwise you won't see much. Stars should be points of light and not have little tails.
I wouldn't rush in to get new eyepieces. They can make a difference, but getting the right mag for the nights conditions, having a well collimated scope and learning to observe detail are the main things to sort out.
06-04-2012, 10:21 PM
Thanks. I have a 10mm and a 25mm ep. I guess I have an UN realistic expectations Based on photos. I assume when a picture of say mars taken through a similar 10" scope is larger due to the focal length of he camera plus the scope yes? I apologise for the 'noob' questions
07-04-2012, 08:18 AM
A lot of those images of Mars and Saturn you see are usually thousands of frames stacked to give one good image , so they give detailes that your eye struggle to see , be patient Saturn will get higher and better , its a bit low at the moment unless you like getting up at 3am !
07-04-2012, 08:31 AM
Its not image quality but rather size i am after. Obviously quality matters, but when i see saturn or mars is dont see anything more than a faint dot. I can see a ring around saturn but it is very small for me to see. And mars is as difficult to see.
07-04-2012, 08:41 AM
Saturn should be more than a faint dot if you use your 10 EP combined with the 2x Barlow. Saturn is small but bright even when using the lowest power eyepiece on my 12" Dob.
Mars is a hard object to hit with too much magnification. I will try it but usually tend to back it off and stick with a sharper view.
What is the focal length of you scope?
How is the collimation on your scope?
07-04-2012, 08:59 AM
FL is 1200 and collimation is good. I have a a-focal picture of saturn i took but its on fb and i have no idea how to get it on this site. My 10mm ep is very difficult to see through as the fov is miserably small.
07-04-2012, 09:17 AM
Welcome to the forum
For planetary observing through my 10" dob (my first proper telescope) I originally purchased a 5mm TeleVue Radian http://www.bintel.com.au/Eyepieces-and-Barlows/TeleVue-/Radian/TeleVue-Radian-5mm/269/productview.aspx
Which at 250x magnification (focal length of scope divided by eye piece focal length- 1250/5) only gave really good views if atmosphere conditions were really steady. About 10% of the time I had the scope out.
So I then purchases a 7mm TeleVue nagler http://www.bintel.com.au/Eyepieces-and-Barlows/TeleVue-/Nagler/TeleVue-Nagler-VI-7mm/191/productview.aspx
Which at around 180x magnification gave good views for most conditions at the expense of smaller image scale.
Now these eyepieces are expensive but, I have collected them over a few years and there are even more pricey variants. There are several alternative brands available at varying prices, you may even pick up eyepieces in the Ice Trade classifieds.
It would beneficial to track down some guys close to you and have a look at the gear they use. (I think there are a couple of amateur astronomers at your local Camera House)
A good quality eyepiece will last you a life time. A bit like having a decent sound system then having crap speakers.
Of course nothing will give you decent views if your scope isn't collimated properly. (alignment of the primary and secondary mirrors). Have a look at this from the Andysshotglass website http://www.andysshotglass.com/Collimating.html
I also have a 13mm TeleVue Nagler http://www.bintel.com.au/Eyepieces-and-Barlows/TeleVue-/Nagler/TeleVue-Nagler-VI-13mm/187/productview.aspx which gives wider views (In my opinion is an exceptional eyepiece). It could be used with your barlow....
There is a lot to digest and everyone one has a different opinion....
07-04-2012, 09:30 AM
25mm EP in your scope = Mag 48x
25mm EP with 2x Barlow in your scope = Mag 100x
10mm EP in your scope = Mag 120x
10mm EP with 2x Barlow in your scope = Mag 240x
If you can work out how to upload an image and give as much information as possible about the eyepiece configuration it would be easier to give feedback on.
07-04-2012, 10:58 AM
Your photo needs to be 200mb or less. (you may need to "save as" and use reduce resolution), Save it to your desktop for ease.
Click "Add reply" bottom left of this thread, (after entering a bit of text) scroll down to Additional Options and Attach Files. Click on "manage attachments".
Click on choose file and then look for your photo's file name in the finder box after choosing your Desktop as folder location (if applicable).
Click the button to choose the file to attach.
Then when the manage attachments box reappears, click upload.
Close this window and "Submit reply".
Hey Presto you loaded an image to this thread.
07-04-2012, 12:01 PM
oh yes i see. i only ever seen the add from web address option. Sorry if its a bit small. this is pretty much what i see using the 10mm. the FOV is terrible so using the barlow seems pointless.
07-04-2012, 05:05 PM
If you don't get any offers from anyone closer, you can bring it out to Bretti Reserve when a group of us (from the Central Coast and Sydney) will be there for a few days around May new moon.
(see thread under Star Parties).
You can try our eyepieces in your instrument, and look though our scopes for comparison.
We can even check collimation etc for you.
Or even come down to Pony Club (Mangrove Mountain) for April new moon if you are up for a long drive.
I was looking at saturn myself the other night, (with a 10" SW Dob) and in the end I was using a Nagler 9mm with a 2x barlow.
That was nice, and is about the best you can expect to get , on a good night.
The Nagler has a big FOV for a smallish eyepiece.
But it is costly.
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