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Posts Made By: Jarad Schiffer

November 20, 2003 01:56 PM Forum: Equipment Talk

Apo's ???

Posted By Jarad Schiffer

I am generally a fan of newtonian scopes (Have a 10", just sold an 18", getting a 14.5"). I also just got an ED-80 (I'm not going to argue whether or not it's a "true" apo....). The reasons I was interested in a small apo were to get a single scope for quick looks and/or travel that could do both wide fields and planets well. Maksutov's do planets well, but can't do wide fields. Achro's do wide fields well, but aren't very good on the planets. small newts tend to be long f-ratio, and again can't do wide fields as well, and the few small fast newts around suffer from large relative secondary sizes.

I have an ETX-90 and ST-80 that I was using as my planetary and wide field scopes, respectively, but I wanted to get 1 scope that could do both. The ED-80 has the additional advantage of a very nice price point, but I was considering something like a used Genesis, Tak or Televue 78, etc. before the ED-80 came out. For quick cooldown, sharp and contrasty views at high power, and wide fields at low power, an APO is the only single scope that can do it all.

Once you get into the larger sizes, the APO starts to lose it's appeal to me except for astrophotography. My big newts have about the same setup time and weight as 6" APO on an equatorial mount, and will show more on both deep sky and planets than any 6". They do give up the wide field, but that's why I plop the 80mm down next to them.....

Jarad

November 24, 2003 09:00 PM Forum: Equipment Talk

Zerodur or not?

Posted By Jarad Schiffer

Get the higher surface accuracy on a pyrex mirror. Zerodur is a low thermal expansion material, but if you are out of thermal equilibrium you still won't get good images due to air currents. If you are worried about thermal issues, install a fan or fans to cool the primary and/or blow air across the front of the mirror (browse through this group and the telescope making group for tips on using fans).

Jarad

November 25, 2003 01:52 PM Forum: Telescope Making

How Short Can the Upper Cage be?

Posted By Jarad Schiffer

Portaball uses a single ring for the UTA on their 10" and 14.5" scopes. I have also seen plenty of ATM scopes with a "frame only" UTA - no solid tube at all. As long as you add the necessary baffles when it is assembled, the only thing the UTA has to do is hold the focuser and secondary in proper alignment, and without too much vibration.

Jarad

December 11, 2003 08:32 PM Forum: Eyepieces

34mm Axiom vs. 35mm Panoptic

Posted By Jarad Schiffer

In several reveiws I have seen, it depends on the speed of your scope. In a fast scope, the Panoptic will win due to the above mentioned astigmatism at the field edges. In a slow scope, the Axiom performs much better and can keep up with the panoptic. If you have a slow scope (more than f8), it is probably a good buy. If you have something much faster than f6, the Panoptic is probably worth the extra money. Of course, this depends on your personal preferences, and how much you are bothered by edge of field abberations.

Jarad

December 23, 2003 03:33 PM Forum: Equipment Talk

Orion ED80 max power?

Posted By Jarad Schiffer

I have an Orion ED-80, and have been trying out a 3-6mm zoom with it (100-200x). So far, I have mostly been stopping at about the 4-5mm click stop (120-150x), depending on the seeing. The image starts to get mushy above that. Maybe if I get a night of really good seeing I will be able to use up to 200x...

So I would say that you probably have a good set now. I would think that the 2.5x powermate might be your best bet, since it should have better coatings and performance than the 2.8x Klee, but try them both and see what looks best.

Jarad

December 30, 2003 03:35 PM Forum: Eyepieces

Worth the price?

Posted By Jarad Schiffer

UO Orthos have widely been described as one of the best bargains in eyepieces. There are several reviews of them and the newer HD orthos on the Cloudy Nights site. The only disadvantages they have are narrow FOV and short eye relief. You certainly couldn't go far wrong with them at around $50 new. Used plossl's are also good deals as someone else suggested, with a bit more field.

Jarad

January 12, 2004 06:28 PM Forum: Equipment Talk

Cooling Fan on 12.5 f/5 Truss Tube Dobsonian

Posted By Jarad Schiffer

Do you mean that you couldn't reach focus, or that the best focus image was fuzzy? If you couldn't reach focus, it could be that either due to collimation movnig th primary forward or back, or due to thermal shrinking of the trusses you can't quite reach the focal plane. If your best focus was with the focuser racked all the way out or in, one of these might be the problem. In that case, try recollimating after you back the primary mirror up or down as necessary on the collimation screws. If the best focus was reachable but fuzzy, then I agree with the others - either collimation is off or you need to cool down more. Bad seeing is also possible - I have noticed that really cold clear nights are often very "twinkly" and not very good for high power work (although fine for faint fuzzy hunting...).

Jarad

January 16, 2004 03:46 PM Forum: Equipment Talk

orion ed80 focuser question.

Posted By Jarad Schiffer

There is no locking screw. There is a tension adjusting screw. I am using it with a 2" mirror diagonal and a 35mm Panoptic, and it holds focus at zenith, although I did have to tighten down the screw pretty hard. I would think that a lightweight SLR would have no problem (OM-1, etc.), but putting something heavy like a Nikon N90 might be tough. The binoviewer will probably be okay without a diagonal, but might be tough with one, especially a 2" one.

Jarad

January 19, 2004 08:43 PM Forum: Equipment Talk

TV-76 or Orion ED 80mm?

Posted By Jarad Schiffer

I have an ED-80, and I have a few comments for you.

Pros:
Optically, the Ed-80 is excellent. It would do a fine job for astronomy or birding. It can provide nice wide field views (up to ~4 degrees), and also takes power well (I routinely use mine at 166x, others have reported 200x with this scope in good seeing).

Price - especially for birding, you will have much less of a heart attack if you drop or otherwise damage the ED-80 than the TV-78. Also, you can buy several nice acessories for the price difference (eyepieces, filters, mounts, etc.).

Weight - the ED-80 only weighs 6 lbs (it is quite large, though - it uses the same OTA as the Orion 100mm f6 achromat).

Cons:
The ED-80 is a bit back-heavy for balance with a 2" diagonal and a heavy 2" eyepiece. For birding especially, I would recommend getting a 1.25" diagonal to make balance issues easier if you plan to mount it using the 1/4-20 mounting block (you will still be able to go down to 25x and a 2.72 degree field with a 24mm Panoptic in a 1.25" diagonal). For astronomy, you will need to get mounting rings or some type of balance plate, especially if you plan to use a 2" diagonal and eyepieces.

The ED-80 is not as solidly built as a Televue scope (in other words, you will you will lose more money if you damage the Telvue, but the ED-80 is more likely to take damage than the Televue from the same amount of mistreatment...).

Hope this helps,

Jarad

January 28, 2004 03:27 PM Forum: Eyepieces

TV Plossls/Powermates: Poor Man's EP Set?

Posted By Jarad Schiffer

Actually, I would recommend doing it a bit differently. The 32 and 25 are a bit close together, as are the 25 and 20. I generally aim for steps of about 1.4x (i.e. sqrt of 2). I would get the 32mm, something around 20-22mm (sorry, I don't have the plossl line memorized for what is avalable), and a 2x powermate. This will give 32, 22, 16, and 11. Then get an 8mm plossl for your planetary use, which will also hit 4mm for those rare nights. You can throw in a 6mm plossl too (which will cost less than the extra powermate) to have finer spacing at the high end if needed. This will give slightly more even coverage of the magnifications.

If that is too much money, I would skip the powermate, and maybe the 22mm. I find that I do almost 90% of my observing with my lowest power and my highest commonly useable power (in this case, probably the 32mm and the 8mm or 6mm, depending on your local seeing and what scope you are using). Lowest power for finding and wide field stuff (big nebulas and galaxies, or galaxy clusters). Highest power for planets, moon, globulars, planetary neb's, small galaxies. The in between ones are only used for mid-sized objects (i.e. medium sized galaxies or open clusters), of which there aren't actually that many.

Finally, would you consider a smaller set of higher quality eyepieces? I highly recommend the 24 panoptic - a great lowest power eyepiece for 1.25" focusers. The 24 Pan, plus an 8mm radian would actually make a nice set, and cost a bit less than the plossl set plus powermates you proposed above. Then you could add others later as needed (2x powermate would still fit in with these, as would intermediate eyepieces, etc.).

Hope this helps,

Jarad


Jarad