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Posts Made By: Jon Isaacs

October 23, 2004 06:42 AM Forum: Equipment Talk

Re: achromatic scope with a high quality –Violet f

Posted By Jon Isaacs

If you were more specific about the scope, the filter, the targets and the magnification/eyepieces, then someone could make a realistic call.

As it is, one is limited to making some guesses... My understanding it that all the filters are only partially effective...

jon

October 27, 2004 04:04 AM Forum: Equipment Talk

Re: Minus Violet Filters** Witch is the BEST**

Posted By Jon Isaacs

Sky and Telescope did a review a while back (this year I think) of just about all of them. One thing to be aware of is that some are fragile.

Jon

November 3, 2004 09:30 AM Forum: Reflectors

Re: Meade ETX

Posted By Jon Isaacs

I can't what its worth. A while back new Meade ETX-90RA's without a tripod were going for about $180. There was some rumour about a large vendor going out of business but for whatever the reason, that depressed the ETX-90 market. I believe I have seen ETX-90ATs with a tripod and autostar for around $300..

jon

December 4, 2004 07:01 AM Forum: Beginning Astronomy?

Re: ALERT: Do Not Pay to Name a Star

Posted By Jon Isaacs

For a different take on Naming Stars I suggest reading Rod Mollise's eloquent comments one the last page of the December Sky and Telescope.

Lets not turn up our noses at it quite so quickly and think that it just might get people looking up at the night sky.

Also there is a similar thread to this on the Newsgroup Sci.astro.amateur that also presents a more leinent view, particularly the post by Sky Tools author Greg Crinklaw... You can find it with searching newsgroups for google.

The Dark Sky Institue offers a competing program the "Adopt-a-Star" which costs $35, comes with some information and supports efforts to reduce light pollution...

After reading what Uncle Rod had to say in Sky and Telescope, I think one has to say "No harm, no foul." Its pretty benign and anything that gets people out at night asking questions and interested in the night sky, well, thats a good thing.

jon

December 15, 2004 07:11 AM Forum: Eyepieces

Re: If they made it, would you buy it?

Posted By Jon Isaacs

Would I buy an 25mm UO ortho??

No...

Just got an old old 18mm UO Ortho in a scope deal and I am far from impressed, must be something wrong with it, disassembled and put together wrong or some thing. My scopes are F4-F7 and only the center of the FOV is sharp, the rest is distracting...

For a 25mm eyepiece, I think widefield, and my old 24mm TV Widefield does a nice job even in some pretty fast scopes, especially with a Paracorr..

jon

December 25, 2004 05:08 AM Forum: Beginning Astronomy?

Re: HELP! CAN'T GET FOCUS

Posted By Jon Isaacs

Have you allowed the scope to cool sufficiently? The C-5 I have takes a significant amount of time to reach thermal equilibrium. Letting it cool with the back open seems to help it stablize.

Jon

December 25, 2004 09:26 AM Forum: Beginning Astronomy?

Christmas Scopes - It's that Time of Year

Posted By Jon Isaacs

Hello Folks,

Up on the Soapbox.....

Yes it's Christmas and its that time of the Year when we may be getting lots of questions about new scopes that people have received as Christmas presents. Many of these will be from people who have never looked through a scope before. Some will be from people who have gotten a very nice scope, but many will be from folks who have been given a simple inexpensive telescope, something that many of us would be reluctant to recommend.

I hope that when responding to questions about such equipment, we all make a serious effort to be positive and supportive. It is easy to go into the rant mode and discuss the many woes of department store scopes, I hope we can avoid that and instead remember back to the time when we were first starting, the excitement, the joy, the confusion. Many of us started with 60mm department store refractors, I started with one I bought at a garage sale for $5.

There is no doubt that these scopes have many weaknesses and are not something that most of us would recommend, but, still, in the end, that $5 garage sale telescope was sufficient to provide the spark that has grown into a consuming passion.

--------

Recently, thinking about this paradox and with Christmas coming, I went to Walmart and spent $50 on the Telstar by Meade 60 AZ-A. This scope is 60mm F11.7 refractor with a plastic 1.25 inch focuser, a simple Alt-Az mount, MA25 and MH9 eyepieces, a plastic barlow and a 5x24 finder.

I have spent several nights using this scope and it is actually quite competent. The long focal length means it is quite color free. The eyepieces are adequate and are all essentially Parafocal including the barlow, a big help for beginners. And surprisingly, the finder actually is not stopped down and is quite good. The focuser is smooth and with care, this scope is definitely functional. In short I have been impressed with what Meade has done for $50.

And I can say I enjoy using this scope. It is sufficiently competent to split double stars like Castor (4arc sec), to show the cloud belts on Jupiter, to see the ring structure of Saturn. But what surprised me was how well it actually does with DSOs. From my light polluted backyard, the Ring and the Dumbbell are reasonable targets. One morning I saw the Crab Nebula. I was amazed at how it showed M93 and I was even able to pick out the Mexican Jumping Bean Cluster from the light pollution. From a dark site, targets like M56 and M71 are quite bright, M76 is on the edge of detection. Many nights after I have put away a larger scope I will bring out this little friend and spend an hour enjoying the color free views of brighter objects...

--------

This scope and others like it, are capable of providing excitement and joy and while they certainly have their flaws, (a shaky-flaky mount) they can do some surprising things.

So, I hope, that as a group we are make the effort to share our knowledge and skill as observers and keep our comments constructive, helpful and nurturing. What makes an Amateur Astronomer is not the equipment that one has, rather the attitude and appreciation of the night sky. For me, if I had nothing else, the Meade 60AZ-A would be enough. I will remember that when answering questions....

---------

Best wishes for a happy time as the year ends...

Jon Isaacs

January 3, 2005 12:13 PM Forum: Eyepieces

Re: SAC Focal Reducer 6.6/3.3

Posted By Jon Isaacs

What are you looking at? Is this during the day?

As Stephen pointed out, you are most likely seeing the central obstruction of the scope. Consider this:

The secondary mirror is about 35% the aperture. This means there will be a dark spot in the center of the eyepiece's exit pupil that is about 35% of its diameter, not necessarily a problem at night.

Here is how the calculation goes:

Exit pupil of 40mm eyepiece at F6.6
= 40mm/6.6= 6mm

That means the beam exiting the eyepiece is 6 mm in diameter.

The hole is about 35% of that which is about 2mm. During the day, your eye only open about 2mm so all you see it the dark hole. At night, it is less likely to be a problem but you can sometimes see the dark spot.

I believe those SAC foca reducers are designed for photography, the camera doesn't have a problem with the central obstruction.

jon

But during the daytime your eye

January 6, 2005 05:41 AM Forum: Equipment Talk

Re: Woodland Hills Camera and Telescopes

Posted By Jon Isaacs

Woodland Hills Camera....

Definitely one of the "good" places to buy. Several years ago I ordered Nikon T mount adapter from them.

It arrived on time but it was the wrong part. I called them, the lady immediately checked the shelf and discovered all the Nikon Tadapters from Celestron were apparently mislabeled.

I was told they would send out the right adapter as soon as they had it and to send the wrong one back when I could... It arrived a few days later.

Dealing with them is a pleasureable experience.

jon

February 11, 2005 10:55 AM Forum: Chinese Optics Imports

BO 101 F5.5???

Posted By Jon Isaacs

Rumour has it that BO is promoting a new short focal length 101 F5.5 scope with some sort of ED glass.

I just wish they would take care of their old promises (102mmF6)first.

I still have my 102F6, waiting for that new "semi-APO" objective.

On the other hand, I have a Celestron First scope 80mm F11 that would benefit from a 2 inch focuser. Maybe now is the time to say "enough is enough" and do a bit of machining to fit the BO focuser to the First Scope. I figure with my 42mm SuperView I would be getting 2.6 degree FOV at 22X. Tentative tests have shown the FOV to be pretty flat and well corrected.

Oh well, I guess its just disappointing to hear of some new scope from BO when somewhere down inside I still had thoughts that they were actually going to come across with the promised goods.

jon :C