Why such a big difference in focal length?

Post by **weixing** » Sun Mar 23, 2008 10:47 pm

Hi,

Premium=Expensive
How expensive?

Usually more expensive than the Orion StarBlast package. Anyway, if you don't observe in low power, wide field, it's should be ok... but that defeat the purpose of getting a fast scope. Basically for eyepiece, select 2 from "good", "cheap" and "wide field"... especially true if you use a fast scope.

I choose the Orion Starblast because i intend to do imaging sometime down the road.

IMHO, that Orion StarBlast package is not suitable for imaging without major modification and you need a mount better than that.

The R135 was shaking just from the wind that day as it was on a camera tripod.

Ya... I think I extend the center column too much... ha ha ha

I believe the Starblast is on a decent mount.

I think the mount that the StarBlast is on will also shake as much when blow by the wind... You cannot expect the Orion StarBlast EQ mount to be as stable as the Vixen Porta mount, because it won't. Basically, you need certain amount of weight on the tripod to be stable.

do not want to limit myself to just planets and bright star clusters. Galaxies, Nebulae are also on my "to observe" list.

You need larger aperture than the Orion StarBlast or better dark sky.

Have a nice day.

Meng Lee · Post by **Meng Lee** » Sun Mar 23, 2008 10:55 pm

Just to add on to Weixing's comments:

Starblast comes in 2 versions, visual and imaging version. The visual version is not suitable for imaging unless you start drilling the tube.

The imaging version does not come to focus easily with eyepieces unless you use an extension tube. (Orion's version is too long.)

Frankly speaking, there are not many scopes that are visual performers and imaging performers. Thats why many of us have more than 1 scope for different purposes.

Razsky · Post by **Razsky** » Mon Mar 24, 2008 12:12 am

Hi all!

Wow, seems like i need to get my facts right again.

Usually more expensive than the Orion StarBlast package.

Wa sian.........................................................................................................................................

Anyway, if you don't observe in low power, wide field, it's should be ok... but that defeat the purpose of getting a fast scope. Basically for eyepiece, select 2 from "good", "cheap" and "wide field"... especially true if you use a fast scope.

But i am intending to use a 2xBarlow with this scope to achieve the 1000mm focal length that i am looking for. With Barlow, speed will be slower right? Then should not matter that much right? Also, if i do have a high quality eye piece in future, i could just take down the barlow and have my F4 back again right?

I think the mount that the StarBlast is on will also shake as much when blow by the wind... You cannot expect the Orion StarBlast EQ mount to be as stable as the Vixen Porta mount, because it won't. Basically, you need certain amount of weight on the tripod to be stable.

Well, maybe not as stable as the porta mount. But i guess decent enough for obbing? But come to think of it, there isnt much wind blowing when i was dwn at WDL with sam doing obs. I guess a windy day means a messed up cloudy sky? Should i take wind into that much concern? Kaos, the most i just take 3 freaking bricks and tie them to the tripod legs! HAHA. (just a thought)

Do you guys have any recommendations for other packages out there? Packages as i feel they are the most value for $$.

I chose Starblast cos i thought it had the most potential. If i wanted speed for imaging (assuming i mod it), it is fast enough. If i wanted focal length, i can just add a barlow and the focal ratio will still be on par with most scope of that range. Just have to get a few more stuff down the road and it will be a decent telescope(eg, mount, finderscope). But for now, below $600, good starter pack i suppose?

Another thing is that i haven used a EQ mount before. Is it hard? Or as plain and simple as a camera mount?

And, is it that hard to collimate a scope?

Thank you guys so much for the comments

Kai Long

Post by **weixing** » Mon Mar 24, 2008 1:51 am

Hi,

But i am intending to use a 2xBarlow with this scope to achieve the 1000mm focal length that i am looking for. With Barlow, speed will be slower right? Then should not matter that much right? Also, if i do have a high quality eye piece in future, i could just take down the barlow and have my F4 back again right?

The image should look better, but you still need to get your collimation right.

If i wanted speed for imaging (assuming i mod it), it is fast enough.

F4 is not just fast... it's very fast and you'll need to use a coma corrector to get a decent sharp image for imaging. But I don't think there is currently a coma corrector available for 1.25" focuser in the market.

Another thing is that i haven used a EQ mount before. Is it hard? Or as plain and simple as a camera mount?

Not hard... just take a bit longer time to setup and heavier than a similar Alt-Az mount setup due to counter-weight.

And, is it that hard to collimate a scope?

Not hard, but very critical for a F4 scope. I'll be in the same situation when I use the Vixen R200SS

Anyway, I didn't use the scope before, so can't really comment on it, but most review for this scope are very positive. Just remember that by getting a F4 scope, you must prepare to accept that:
1) there might be serious coma issue at low power, and
2) the image may not look sharp at higher power if collimation is not accurately done.

Have a nice day.

Razsky · Post by **Razsky** » Mon Mar 24, 2008 1:59 am

Hi!

I shall learn collimate!!!!!!!!

What is comma?

Did some search and couldn't find ans.

Kai Long

Razsky · Post by **Razsky** » Mon Mar 24, 2008 2:01 am

K. FOUND IT.

I typed COMMA. [smilie=ahaaah.gif]

Will go read up!

Razsky

Meng Lee · Post by **Meng Lee** » Mon Mar 24, 2008 2:17 am

You can consider this set also:

http://www.telescope.com/control/produc ... t_id=09182

This has a decent focal length. Decent aperture. Decent accessories. And next time you can dismount the tube for planetary imaging and collimation is less critical.

Razsky · Post by **Razsky** » Mon Mar 24, 2008 2:23 am

Hi,

Well, it does solves the mount issue! But alot bigger right?

I think i really prefer a smaller reflector. Then can carry it wherever i go. Perhaps even join you guys in the mersing trip. Haha

Razsky

Meng Lee · Post by **Meng Lee** » Mon Mar 24, 2008 2:27 am

http://www.telescope.com/control/produc ... t_id=09804

This is the 114 version and longer focal length. But the 6 inch is probably the height of a primary 4 student.

Well, carrying a bit more things makes your astro hobby far better, I think its worth it.

Post by **acc** » Mon Mar 24, 2008 9:05 am

I second Meng Lee's recommendations: Go for the XT6 if you think you can manage it (its not really that big or heavy and if you are going to be out with a scope for OB, might as well carry something that shows u more

).