Posts Made By: Bob Young

Normally, just before shutting down for the night, I check the objective with a flashlight to see if there's any dew on it. Normally there isn't so I cap it and leave it capped while the rest of the scope dries out inside. Always figured that if I uncapped a cold, dry objective inside, it'd probably fog from the temp. difference.

Last night everything got soaking wet but the objective stayed clear (I use an extra slip on dewshield). Was concerned that the dewshield flocking on the TV102 may have gotten soaked so, once inside about a half hour and somewhat warmed up (not totally), I unscrewed the cap and found the objective fogged. Of course I left it open and the moisture left no traces once it evaporated. Was glad I didn't leave it sealed up with the moisture in there.

Anyway, how do the rest of you do it? Do you always uncover the objective when back inside to be sure it dries? Or, do you assume that if it was dry when you put the cap on, it'll stay dry when it warms up?
Bob

I've noticed on the TV site that the formula given for TFOV in degrees is: (e.p. field stop dia./scope f.l.) times 57.3.

Somehow I've gotten in the habit of calculating TFOV as:
e.p. Apparent FOV in degrees/magnification

The two aren't the same. Usually they're close, but in some instances there's a significant difference. The Apparent FOV formula seems more useful as e.p. AFOV is usually given, whereas field stop diameter isn't.

Is the AFOV formula technically valid? Can anyone point out circumstances where the AFOV formula shouldn't be trusted? I suppose vendors could be fudging their AFOV figures a bit.

Found this posted this morning at the Takahashi Yahoo group. It's from Art Ciampi. Search didn't turn up anything about it here, so thought I'd start a thread. Might be just the thing for a visual observer or an imager who wants near 5" performance without dealing with a really big scope like the TOA130.

Announcing the TSA-120/120mm Takahashi Super Apochromat.

TSA-120 SPECIFICATIONS

* Second TSA triplet apochromat
* Very high order of color correction
* Compact design only 28" long collapsed
* Long back focus 227mm [8.93"] to accommodate bino viewers and any 2" diagonal
* Supplied with 2" and 1/1/4" accessories and extension tubes
* Quick release finder bracket included
* Knife edge baffles are standard for highest contrast

The TSA-120 is the second triplet apochromat in the TSA Series. Its superb color correction will provide high contrast images with pin point stars across the field.

The compact size of 28" allows the TSA-120 to be easily transported to remote sites.

The TSA-120 is a great scope for imaging. The TOA 35 flattener converts the 120 into an f/7.3 882mm flat field 2.6º instrument and the reducer changes it to an f/5.6 672mm

Mechanical Specs

Diameter of main tube: 125mmø
Diameter of dew shield [sliding]: 713mm? [28"]
Weight of OTA : 7 kgs/15.4 lbs
Back focus: 227.5mm [8.93"]

Optical Specifications

Aperture: 120mmø
Focal length: 900mm?
Focal ratio: f/7.5
Optical design: Triplet ED apo
Coating: Broad band multi-layer
anti-reflection coatings

TOA-35 Flattener

Focal length: 882mm
Focal ratio: f/7.3
Optical performance 7 micron RMS-spot
to 20mm off-axis
Image circle: 40mmø
Image field: 2.6ºø diameter

TOA-35 Reducer

Focal length: 672mm
Focal ratio: f/5.6
Optical performance: 4 microns RMS-spot on axis
6 microns 10mm off-axis
13 microns 20mm off-axis
40mmø/3.4º field

Price: $3795 MAP

Hi all,
Wondering which design is likely to cooldown the quickest and which is least likely to develop issues operating in subfreezing temperatures (down to about 0 deg. F.). The specific scopes being considered are the new TSA120 and the NP-127.
Thanks.
Bob

The following is from the OPTCorp listing describing the NP127is:
"The Tele Vue NP127is just got a make-over! Both the optical and mechanical designs have been revised to further reduce atmospheric defocusing ability.

"A new lens prescription delivers smaller spot sizes over a broader wavelength, a stainless steel lens cell provides better thermal stability, and advanced multi-coatings maximize contrast and transmission.

"The new Televue NP127is telescope has a new 10:1 focuser pinion assembly, and a longer captive dew shield and strikes quite a pose with gloss black anodized metal on the dew shield and rear cell.

"While all these changes are welcome, the new NP127is kept its predecessor's fast f/5.2, flat-field optics and the ability to image across a 52mm diagonal sensor. All Tele Vue imaging system accessories are compatible with the new NP127is."

Looks like Televue's flagship refractor got a facelift. Anyone know more about this? Has the 6:1 Focusmate been replaced with a FeatherTouch or have they come out with a 10:1 Focusmate? The stainless lens cell appears to be new as well.

Haven't seen much discussion of this.
Bob

To get satisfaction from astronomy, you have to make progress. Progress, requires regular observing sessions. To observe regularly, you need a convenient observing environment. The scope is at least 50% of that environment. The remainder is the observing site. Be it ever so humble/light polluted/obstructed there's no place like home; 'cause that's normally where you are when it gets dark. An imperfect scope at an imperfect observing site that will be used 3 or 4 times a week is much better than visiting the perfect viewing site with the perfect scope once a month.

The scope that has given me the most satisfaction is a Meade ETX125. The Meade has many warts, but optically it gives up little to my TV102. It's versatile. GoTo with Autostar or NON-GoTo with hand paddle. Alt-Az mount or Polar mount(using wedge) on #887 tripod are both reasonably stable. I've settled on non-GoTo operation with scope polar mounted. It tracks targets quite well with rough polar alignment. With the obstructions around the yard, a good alignment for GoTo operation would be impossible. It's mounted and ready to be carried outdoors at any time. Height is good for seated viewing, especially with a Starbound chair. Scope's moment arm is short so swinging between widely separated targets doesn't require much furniture movement to get comfortable again. Using the hand paddle the scope can be nudged into the desired position with good precision....however, the infamous ETX gear backlash IS aggravating. Because the axes are locked, there's no problem with the scope wandering off target when you change eyepieces. However, for all it's good qualities, I will probably replace the ETX with an LX90 on a wedge in the future IF an LX90 can be made to track in polar mode without a star alignment and IF it can be moved easily when mounted on its tripod. GoTo will be for showing the astro-sights to others.

Up-thread someone said that once you have had a Dob you'll never go back; or words to that effect. It wasn't true for me. My first scope was a 10" Dob because I thought it optically gave me the most "bang for the buck". However the frustration of getting it on a target and keeping it there caused me to abandon astronomy for a time (I AM a card carrying Klutz). I'm tempted by those sweet looking PortaBalls; but I know they're NOT for me. The lure of the ETX's GoTo brought me back. Then the ETX taught me how to get around the sky without GoTo. That was PROGRESS.

It's been said that the best scope is the one you'll use the most. A far-from-perfect scope turned out to be the best for this beginner.
Bob Young

Thanks, everyone, for the inputs. Some things I hadn't considered were brought to light. If I decide to go ahead with this, I'll post the results.

The question about how effective the astronomy will be on a trip of this nature is a valid one. Something that seems workable from the security of a comfortable chair in a cool carpeted room might be an expensive joke when mixed with mud, bugs and bad weather. But, then again, if bugs or an uncomfortable air mattress are keeping me awake half the night anyway, I might as well log some eyepiece time.

Thanks again.
Bob Young

I have followed this thread with interest, but have been left with some questions:

1)Having had good luck with Meade equipment and a natural predeliction for buying American, I would like to know how the Meade product stacks up against the Russians. I actually prefer the Meade's f/15 focal ratio.

2)I'm aware that Meade puts a 'big hunk of lead' in the back of the fork mounted 7" Maks to achieve balance on 8" fork arms but wonder if the OTA version of this scope includes the lead weight as well. Comparing the 7" Mak OTA weight against the 8" Meade SCT OTA weight, the difference is only 3 lbs. (Mak heavier). I've heard that there is (or was) a 'Spotter' version of this scope that was made without the lead. Is it still available?

3)If the Russians are the clear winners, how does Lomo stack up against Intes?

Thanks.
Bob Young

David:
I've owned a TV102 for about a year now and will attempt to address at least one of your questions plus throw out some unsolicited opinions on the Gibraltor:
1)The green focuser and dew shield of the green/white TV102 is painted; probably powder coated. It's not as durable or as expensive as the black anodized shield/focuser on the black & white model.
2)& 3)Cannot help you here; unfamiliar with Sky Tour

For what it's worth:
I owned a Gibraltor about 2 months and got rid of it at the first opportunity. Too difficult to find and track objects, especially at anything over 100x. Staying on a target required continuous manual motion inputs on two axes. As the magnification went up, the inputs had to be very precise or you were off the target. Sky Tour would be some help in getting back if you did wander off, but still the inputs would have to be precise.

Changing to a high power eyepiece once an object was acquired was also a hassle. Even if both eyepieces had the same weight, the tube was unbalanced in the interval between e.p. removal and e.p. insertion. This meant that at least the altitude axis would have to be locked. If you're a little klutzy like me, it means both axes will have to be locked. Once your high power, small FOV e.p. is in place, you have to unlock the axes and try to catch up with your object again. But now, due to the high mag., your inputs must be much more precise. In my case, the change to a high-power e.p. was usually the last I saw of my object. In retrospect, a zoom e.p. would've been a big help with this mount.

I ended up putting the TV102 on a used GM8. The GM8 is overkill, but it can track objects under motor control with axes locked which eliminates both the tracking hassle and the e.p. change hassle. Precise movement on both axes can be done under motor control. I don't have GoTo or digital setting circles on it, but for visual use; just pointing the RA axis in the direction of Polaris is all that's needed. Nowadays the new Meade LXD55 mount would probably be a better choice than the GM8 for strictly visual use. It would cost much less while providing GoTo and Dig. Setting Circle capabity.

The GM8 had one unexpected benefit: Its stout construction just begged for more of a load. Ended up buying a very nice used C9.25 OTA for less than $1000. I use that for DSO's while reserving the TV102 for the moon, planets and wide field use. Of the two the C9.25, once cooled down, is much more impressive than the TV102. I've been underwhelmed by the TV102. I keep it primarily to give some future immunity to the APO bug. A 4" aperture just isn't enough.

Knowing what I know now I'd take advantage of one of the Meade or Celestron sales and not look back. You might put off an APO purchase until you've had experience with someone else's and and can determine with certainty that's what you want.

Hope this helps.
Bob Young

Thanks for the report Tom. Been contemplating putting my TV102 on an LXD55 since the mount was first announced.

A few questions occurred to me:
1)How transportable is the mount/scope combination? In other words, with the scope on the mount and ready to go, can you readily pick up the whole thing and carry it out of the house?
2)Did you use the TV ring and a dovetail plate to attach scope to mount, or some other arrangement? Were all the parts off-the-shelf?
3)Is it possible to put Autostar in 'tracking mode' (i.e. run the R.A. motor at sidereal rate) without bothering to do an alignment? This would be my 'quick-look' approach.
Thanks again.
Bob Young