Getting started

[dougdoug]

Hello all. My name is Doug and this will be my first post.

I have been researching telescopes and have decided on a Dobsonion. This will be my first real (not $99 from the department store) telescope. Had one, and gave it to my Granddaughter.

Originally I thought I would go with an 8” from Orion.

The more I read, the more I want to get the 10” for the extra light gathering ability.  I also know myself and would immediately wonder if I made the right choice.

A few things concern me. Number one is Collimation. From what I have read the 10” will require collimation more often. Some say every time you move it. So, would moving it in two trips from the garage to the yard require re collimation or are they talking about moving it in an automobile?

This brings me to another question. Laser collimators. I have watched videos of people using them. They seem simple to use. However, I have also read a lot of negative reviews claiming they can cause more problems unless they themselves are properly collimated. These same reviews claim a Cheshire is the way to go. So, I’m a little confused as to which to order.

One more question is regarding Coma. I understand this might be a problem with the 10” Orion being an F/4.7.  Others say anything slower than F/4 shouldn’t be a problem.

Hopefully someone can answer my questions. I will appreciate any advice or comments. Thank you very much.

 

[cletrac1922]

Welcome Doug from land down under

I have a 10" Skywatcher collapsible dob, and find collimation not an issue

Do you intend to travel much with your scope, or just backyard observing

Reason I ask, belong to an astronomy club, and out 2 or 3 times per month doing displays for primary schools, space badge scout/guide movement

Very rarely need to collimate, and when do I use a laser collimator

Never used a Cheshire

Scope easy to transport, and takes only a couple of minutes to set up

John

 

 

 

[dougdoug]

Thank you for the reply John. Sounds like I might be over thinking the collimation issue. I will spend most of my time backyard observing. I live in the country so light pollution shouldn't be a problem. The closet town in about 7 miles away with a population of around 7000. No astronomy club. There are a couple of colleges not to far from here and I may check with them. I have been looking at the SkyQuest XT10 plus. Thank you again for your response.

[laudropb]

Hello and a warm welcome to the SGL.

I would not be too worried about collimating. It is not as difficult as it looks and once mastered is no problem at all. If you are just moving the scope out to your back yard it will seldom need more than a little tweak if at all.

As for coma, I would not think it would be a great problem in that scope. I only have an 8 inch Dob and visually I have never really noticed it.

A 10 inch Dob is an ideal starter scope in my opinion and will give you many years of service.

[Buzzard75]

I have a 12" truss type dob. Collimation is a piece of cake once you get the hang of it. Anytime you setup your scope, one of the first things you should do is check the collimation. Even small bumps can knock the secondary or the primary mirror out of collimation. A fraction of a millimeter of movement by either can mean even greater error over the focal length of the tube. As I have to disassemble mine every time, it's a given for me. Sometimes it's off a hair and I don't bother with it, other times it's off by quite a bit.

Laser collimators are great and I use one. They make collimation a little bit quicker. They do need to be checked for collimation from time to time, which is also easy enough to do. I do recommend you get yourself either a Cheshire and/or use a collimation cap though, for two reasons. One, you'll need it for alining the secondary with the focuser. You can't do that with a laser. Two, knowing how to use a Cheshire and/or a collimation cap will help you better understand the collimation process. I will often times collimate using all three to check, double check, and triple check my collimation. Is it absolutely necessary that I check it with all three? No, but since I primarily use my laser, if I check with the other two, I know there's nothing wrong with my laser. If I check with the Cheshire or the collimation cap and it's not right, I know I need to recollimate my laser. But since I know how to use a Cheshire and collimation cap, I'm not dead in the water.

I've recently had my first experience with what I believe to be coma. I only experience it with a long focal length, wide FOV eyepiece. I don't have a problem with my other eyepieces. I haven't yet checked to determine if what I'm seeing is coma or if it's astigmatism. My guess is coma at this point. I honestly wouldn't worry about it until you actually experience it. In my case, it's just a specific combination of eyepiece and telescope and isn't always a problem and it may not be for you either. Even if you do see it, it still may not be such an issue that you feel you need to spend the money to correct it.

[Pondus]

Hello Doug and welcome to SGL .

Orion XT10 plus sounds like an excellent Choice. I`ve got the XT8i myself and find the Mirrors to be very good.

I bought mine second hand, and I rarely have to collimate the mirrors, only a slight tweak  on the primary once in a blue moon. And I do carry it up and Down stairs.

Never touched the secondary.

Although I do check the collimation before every session (takes 2 mins tops) using a Chesire. Never tried a laser collimator.

 

Good Luck With Your first 'proper' Scope .

 

Rune

[dougdoug]

Thank you all for the welcome and information. You have eased my mind and helped me make up my mind. I am going to go with the Orion 10 inch and a Cheshire eyepiece to start out. Thanks again all.

[cletrac1922]

Last Saturday night club meet, had a new member came along with a 6" solid tube dob, and commented not able to see anything as blurry, and had brought second hand on E-Bay

I had a quick look, and had my laser collimator in my eyepiece case which was in the car

Found was way out, and had issues trying to collimate

Was looking at the secondary mirror, and something did seem right

Notice vanes holding the secondary mirror were warped and twisted

Using a bit of paper and pen, measured distance from centre mounting screw to edge of the tube

Secondary mirror was over to one side by a fair bit

First time every seen that

Assume previous owner had been trying to do some sort of alignment and stuffed it totally

Adjusted secondary mirror where should be, with mounting screws for vanes, and bingo, perfect collimation

Very happy new member