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Newbie Help

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#1 Guest_**DONOTDELETE**_*

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Posted 08 August 2003 - 08:53 AM

Since I have had a full week of my new 8" reflector telescope I have noticed some things that I cant explain.

Why is it when an object is right in the middle of my eyepiece its very bright and has kind of a starburst effect, but when its out towards the side of my view, that same starburst is gone and it looks like a dot again?

How much does moon brightness play into viewing things? Its been very bright all week. Ive noticed some weird ghosting effects I think that are from the moon that my telescope seems to pick up.

Lastly, I have been hunting for pluto. I have a good idea of the general location of where its at (I think). What power should I be able to see this at or is the moon brightness going to keep me from seeing it since its close to the moon somewhat? I want to be able to make out a planet and not just the light from it. Is it realistic to find this with what I have? (8" Diam, 750 Focal length)

#2 Guest_**DONOTDELETE**_*

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Posted 08 August 2003 - 01:13 PM

Regarding #1- I would ask whether or not you have collimated the scope since you've had it for a week.

Regarding #2 if you are out of collimation you will see funny things. Also if you are using inexpensive eyepieces you can get internal relections.

Regarding #3- Pluto at this time is at 14th magnitude and has a disk diameter of .14 arc minutes...8.4 arc seconds. I doubt the you could resolve this small of a disk with an 8" f/4 scope. Are you sure of the focal length? 750mm=29.5"

You will need a program like The Sky or something similar to see what the field of view looks like in the area of Pluto and try to locate it that way. Imagers take a picture of the area then take another several days later and blink the two to see the planet's movement.

Lenny

#3 EdZ

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Posted 08 August 2003 - 01:25 PM

Lenny,

I think Pluto may have an apparent diameter of 0.84 arcseconds not 8.4. 8.4 would make it 1/3 the size of Mars right now!! It is definitely not that.

edz

#4 Guest_**DONOTDELETE**_*

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Posted 08 August 2003 - 01:54 PM

Quite right. I meant to say .14 arc SECONDS not arc MINUTES.

#5 Guest_**DONOTDELETE**_*

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Posted 08 August 2003 - 07:17 PM

I havent collamated my scope. I just found a website that sells some kind of laser adjustment tool for 70$. Is this an investment Im going to need?

I dont think its poor optics. I think its something else. Like I said its on my finderscope only and not on the actual eye piece when I look through (as far as the ghosting effect)... I think the alignment might need to be done like your stating above...

It has a focal length of 750mm and its diameter is 150mm (says so on scope). That makes it an F5 right?

Whats a good observation to make for a beginner (other than the moon of course)?

Also, one last question is, when I use this program, it shows pluto with a distance of AU (astronomical units) and then it shows something else with a LY (light year). Is an AU closer than an LY? Or are they similiar or ????

Thanks for the help Lenny!

#6 Guest_**DONOTDELETE**_*

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Posted 08 August 2003 - 08:32 PM

No. You can collimate without using a laser. As a beginner save your money.

You said: "Why is it when an object is right in the middle of my eyepiece its very bright and has kind of a starburst effect, but when its out towards the side of my view, that same starburst is gone and it looks like a dot again"
That doesn't say it's your finder scope. With a reflector scope you will get diffraction spikes caused by the vanes that hold your secondary mirror in place...usually four spikes. This is probably the "starburst" you are seeing. It's more apparent on brighter stars.

Yes it's an f/5 but 150mm is 6" not 8" I have a similar scope I use for wide field observing.

Mars, the Moon, star clusters, globular clusters, there's a ton of things to see right now. Check out the area of the Milky Way around Sagittarius. Get a copy of Sky and Telescope or Astronomy magazine and use the star charts in the center.

An AU is the distance from the sun to the earth...93 million miles on average. Objects that are VERY far away require a different unit of measurement so astronomers use light years, the distance light travels in one year at 186,000 miles per second. A light year is about six trillion miles if I remember right. Thats 6,000,000,000,000 miles, a far piece.

There are planetarium programs for your PC that are free and some that run several hundred dollars. The Sky is one of the more expensive. I would recommend Earth Centered Universe (~$90) or Cartes Du Ceil at http://www.stargazin...ropc/index.html for free.It's written by a French man but it's in English and very complete.

Enjoy-

#7 Guest_**DONOTDELETE**_*

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Posted 08 August 2003 - 09:31 PM

Yes you are right. I ment in my finder scope is where i see the ghosting images. Sorry if this mislead you. I do see the starburst effects as you described. I will look into getting it adjusted.

You are correct. I bought this used off of ebay it was listed as 8". I took it for granted that was what it was. It is not as I have measured. It measures 7" across exactly... great... more depressing news...

#8 Guest_**DONOTDELETE**_*

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Posted 09 August 2003 - 08:24 AM

Well finders are inexpensive and often not very good quality but then they really don't have to be.

I assume it's a commercial telescope. What make is it?

Is it a Dobson mount or did it come with an equatorial mount?

Did the seller represent it as an 8"? I'm not familiar with how EBay works but you may be able to return it if it's not as advertised. Often it's "buyer beware" so I avoid it like the plague. I've had better luck on Astromart.



#9 Guest_**DONOTDELETE**_*

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Posted 10 August 2003 - 03:33 PM

I took it to my telescope shop here in town. Its the closest one to me (about a 45 minute drive)... They did a laser alignment on it, they said it was slightly off. They suspect that the light from the moon was hitting the finder at the angle it was at and thats where my ghosting was coming from.
The said this telescope is a very good telescope, much better than what they see come through there shop. I have not been able to find it online, it says "Event Horizon" on the side of it. It was listed as an 8" on the website. I paid 200$ for it, and 30$ to ship.
They did suggest some filters so I bought some to help with the atmosphere they said which was more than likely causing my problem.
Just need to play with it some more. Just a little disappointing is all. Ill have to watch Astromart...



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