Posts Made By: Ron Sowers

Anyone ever compared, either side by side or just from past experience, the difference in detail and sharpness between a 5-6 inch MAK and a 8-12 inch reflector?
I know optical quality is a huge factor, but just wondering with the average samples out there, how they compare.

What I'm wondering is this. I know more aperture = better resolution and personally my 10 dob has shown me the most on planets, BUT, thinking in arc seconds, are we really using a large scopes resolution or is it merely the added brightness causing small dim features to show up that might be there in the smaller scope but go unnoticed?
(example, anyone ever calculated the size in arc seconds of a certain loop or festoon on Jupiter to know just what theoretical aperture would be needed to detect it?)

How much CAN you see in a GOOD 5-6 inch MAK?

Just curious!
Thanks!
Ron

In relation to the other thread I started "Big reflector VS smaller MAK", anyone who has really used a 5-6 inch MAK, what were the finest details you can remember seeing on, say, Jupiter or Mars?

Thanks!
Ron

After all this talk about Maks Vs reflectors, etc. I took an image of Jupiter into the aberrator program and generated some samples. I wonder how accurate this software is?
Seems to show that F-ratio makes more of a difference than obstruction size.

I enclosed a pic here,
First pic is raw image
Second is my scope, 10 inch F5.6 about 20% obstruction (amazingly is exactly how I see Jupiter in my scope in good seeing, hoping that means the rest are accurate too)
Third and forth images are 6 inch scope F10, with both 20 and 35 percent obstructions. The 6 inch with 35% looks a bit better than the 10 inch F5.6 as far as sharpness and contrast.

Thoughts on this?

Thanks, Ron

OK, I thought I'd try one last line of questions here. Included is a pic that is close to my best view of Jupiter with my 10 inch dob on our best night of seeing. The best view was at about 272X even though I could observe at over 500. It was probably a teeny bit more sharp then this, I could see a bit more of the tendrils hanging off the bands than this shows. But it's close.

Here is the question: What is the smallest scope you honestly could see Jupiter this well in?

Last night I observed the moon, and then decided to do some tests, maybe this will shed more light on things..

Atmosphere
Our skies started at about a pickering number one, horrid while the atmosphere was shedding heat. By 11:40 things looked more like the number four on the pickering scale (I think).

Collimation
I really checked collimation, I'm thinking I might not be as well collimated as I thought I was. Took me 25 minutes to get things really collimated on Polaris. One thing I noticed about my laser, if I bump it or move it, the dot shifts. I was checking it before ona star at about 140 X, but last night I checked at 272 and could tell collimation was still off, so that's where I ended up tweaking for 20 more minutes. Apparantly even using the barlowed laser method doesn't get you as close as I thought.

Star Test
I did a star test at 272, I can BARELY see any difference between inside and outside focus images. I got Suiter's book out and compared. The images look at least as close as his example of 1/8th wave.

What does this mean guys?
Are all my problems due to atmosphere and collimation?
(I know, just like you guys were saying, oops)

Thanks!
Ron

Today I messed with collimating the laser again,(according to Floyds article) I did this yesterday and was so frustrated as I couldn't get repeated patterns. Today I made 8 marks around the barrel of the laser, set up a vise and used the top part of my barlow for a tube to hold the laser. I put a piece of paper on the wall about 20 feet away and carefully tuned the laser to each mark and marked a number on the paper to represent each number that it was turned to. The problem I believe is that the plastic barrel of the laser is not ROUND! It must be ever so slightly mis-shapen. Grrr. No wonder I'm always tweeking the alignment of the secondary!

Note the attatched picture. It shows the laser, the numbers I put on it, how I held it and the crazy pattern it makes when rotated. It should make a circular pattern. ( I was very careful also to tighten the set screw the same amount after each rotation.)

Do not ever buy a cheap laser!

Ron

Hey Folks,

Well, after much (and I mean MUCH) suffering trying to fix this laser, I am happy to say I did it! Sheesh, what a pain that was! But it is dead on straight with zero shift at 22 feet distance. Yeehaw! For any that don't remember the other thread for didn't read it, I bought a 'budget' laser years ago, it was made of one piece plastic. (not quite as cheesy as it sounds but not 'good' either). After reading Floyds article on collimatin a laser the fun began!

What I ended up doing (going through)
I ground down the plastic barrel that inserts into the focuser, it came out crooked, ugh. So I finally got smart and took the laser out of the assembly leaving it empty. I put a drill bit on the drill, chosen to fit snug in the bottom hole and used the collimation bolts of the laser unit to grip the the drill bit. I then turned on the drill and watched for wobble, and used those bolts to align the assemble so it spun evenly. Now I had basically a lathe. So I put a razor blade in the vise and carefully ground the bottom of the laser as true as I could. Then I used an eyepeice barrel from an extra old Plossl and put that over the bottom, aligned it and glued it. Now I had a laser with a nice metal ROUND barrel. Yay! I re-inserted the laser unit and began the collimation of the laser process.

Collimation

Here is where things got fun and where I thought I was going to do something even better than what Floyd suggested. He says to use a V-block, I thought "V-block, that doesn't sound good, I'll use the barrel of my barlow lense, or the 1.25 adapter ring from the focuser".
Oh no, that is NOT good, that little bit of play in those (even though I swore I had none) messed me up like you wouldn't beleive. Last night I made a V-block, for my last try at aligning it. And "Lo and Behold" it worked perfectly. It was so easy to rotate and keep it stable. (Maybe Floyd should edit his article for people like me and say, "USE a V-Block DO NOT try using your barlow or adapter ring!!!!" )

End product

Now it's dead on perfect as can be. I had bought a cheshire this week also, and man, I cannot see HOW you can get the secondary pointing at the primary center as accurately with that, as you can with a laser. I stare and look, it looks good, but I can twist one of the secondary screws a bit and things still look right.... or do they... hmmm, argh! I think I will do what someone else suggested on here and that's use the laser to adjust the secondary and the cheshire to adjust the primary.

Whew, what fun this was!

Ron

While I'm on this, "getting things as good as I can" adventure, I've been wondering what I can do about the mirror clips. Any good ideas on getting rid of them and still having the primary SAFE in it's cell?

I was thinking of just removing the hangover tab deal and using that really strong silicone stuff, (RVT or R..something) and using it to glue the side of the mirror to those side posts that the tabs are on. Just not sure if it would be safe on a car trip with that. Anyone done anything like this?

Ron

Man, I am loven this device. I'm not sure how close a GOOD laser gets collimation, but this cheshire is awesome. I can't wait to get a look at the gas giants now

Last night I collimated with the cheshire, took my time and got it spot on, then went out and did some observing. Towards the end, I remembered I wanted to see just how close it was. I pointed at Polaris, checked at 258x... perfect, put in the barlow for 517.. still perfect, pulled the 5.5 back in the barlow for 2.5 times effect for about 646 power, still perfect. Even IN focus. I could see the star with a little ring around it. I've NEVER had this level of collimation before. No more running back and forth, tweeking while trying to re-find the star. Cheshires rock!

Ron

(thanks for talking me into getting this Bob C.! )

I wasn't sure where to post this, so thought I'd try here since I guess our computers are also our astro equipment

Anyone know of a free downloadable star chart that actually works?
I've searched and found some, some didn't work, one was like a quick trial, etc. Doesn't have to be fancy, just show the basic M objects and planets

Thanks!
Ron