The SIPS (aka/ Focuser Mounted Paracorr2)
By Dave Bonandrini
Stock introduction: For those of you who don't know me, I build large Dobsonian telescopes as a hobby. My definition of large is 24" and up. I teach telescope building classes that emphasize the reasoning behind doing something a certain way, rather than just following a set of plans. I consider myself a more than competent woodworker. I am an AstroMart Moderator, and I currently use a 30" f/5.3 Dobsonian telescope that I designed and built myself. The largest telescope I have built is a 36". I have owned or used almost every brand of Dob in the world, and then some.
Yes, I have been called "nitpicky", and yes, I acknowledge that my reviews are often lengthy. These products are not inexpensive; so I certainly will point out every benefit and flaw I see. My reviews are not length constrained like the 1000 word reviews seen in the glossy magazines, nor do I need to protect advertising revenue, so I try to cover everything with no artificial sweeteners added.
Like gossipy girls in a school yard, many people murmur that if somebody likes a product they review, they are somehow "on the take" or "have a relationship with" a manufacturer. I have no interest in any astro related company (other than giving them much of my income) .
WHAT IS A SIPS?
The new SIPS (Starlight Integrated Paracorr System) is an interesting graft of a product. Televue made the optical group, and Starlight Instruments (the maker of the FeatherTouch focusers) engineered and manufactured the body.
It has been eagerly awaited by many in the hobby for some time now for a few reasons:
1. The Paracorr 1 was introduced before the making of mirrors faster than f/4 was popular. Nowadays, reading online about mirrors made at crazy sub f/3 speeds seems almost commonplace.
2. Most people like to say that the Paracorr 1 runs out of correction at f/3.5 (although I've tested it at f/3.3 and it still does a decent job).
3. The Paracorr 1 had an adjustment slider that had to be set for each eyepiece. It came with a chart for all of the Televue eyepieces that were available, so you would know where to set the slider. If you had a non Televue eyepiece, you had to experiment by looking through the eyepiece while tuning the slider.
4. Newer eyepieces have become available since the Paracorr 1 was designed, so correction for the newer, wider field Ethos line is not optimized.
The SIPS is said to address all of these issues. The SIPS supposedly does a good job correcting down to f/2.8 (although I will not have any optic even near that ratio for this review), it is optimized for the new Ethos eyepieces and it does not require any adjustments when changing eyepieces.
The SIPS will allow a f/3 telescope to perform like a f/12 telescope. It also creates a small magnification factor of 1.15x (as did the old Paracorr) .
I should make a few things clear before we go further. You need a recent model Feathertouch focuser with a 1.5" length drawtube. It is not going to fit any other brand or model. Most of the better brands of telescopes only use the FeatherTouch, but double check brand and model size before you buy. If you need to replace your focuser and buy the SIPS, it is going to set you back over $1000 USD. The SIPS alone runs $625.
Another thing to note is you need to remove the SIPS lens array every time you collimate your telescope.
The Paracorr 2 is also available with the tunable top adjustment slider, just like the older model.
CONTENTS OF THE BOX:
The SIPS unit releases the lens element so that you can collimate without the lens in the lightpath.
You get a positioning aid, that assists you setting up the primary to SIPS distance. This distance only has to be set one time.
The SIPS and the Positioning Aid were both well wrapped in many layers of bubble wrap and clear packing tape. This is always a welcomed sign to see very well protected products.
Finally, you get a CD-ROM with the instruction manual on it. The CD had a label placed off to one side that made it too off balanced to work in any of my DVD-ROM drives. The drives just spit it out like I fed them poison or something. I had the dealer email the manual to me.
Upon removing the Dust Cap, I saw not only dust, but finger prints, on both the front and rear elements.
Although Televue lens coatings are famous for being pretty tough and easily cleaned, I expected spotless optics. I called the Televue dealer who I got the SIPS from and they opened other units and found more of the same. I understand that Starlight is a machine shop, not an optical shop, but they still should set up a clean room for assembly and buy some cotton gloves.
The next obvious thing I noticed was that there were no setscrews included with the kit to assemble the unit. I again called the dealer and they looked and found the same thing on the other units they had in stock. A small oversight, but if you are not a handy person with a cabinet full of nuts and bolts, it will mean a trip to the hardware store.
A quick check with a gauge showed the setscrews needed to be 6-32. I was glad they were not some obscure metric size, because there would be no place local for me to buy metric setscrews on a Saturday. I already had 6-32 in my possession. I'm certain that this oversight will quickly be fixed, but if you find yourself in the same position, you want to ask for "6-32 stainless steel setscrews, cup point (not cone point)"
If you only lived your life online, you might think that every large new Dob is a f/3 or lower. It seems that way because those are the cutting edge scopes that get all of the attention. In reality, it is fairly hard to find a scope faster than f/3.6 . The fastest scope I could find anywhere within driving distance was f/3.3 . I apologize if you wanted to read about how well the SIPS corrected a f/2.5 or f/3 telescope; I'll add on an addendum to this review should I find such a beast.
To install, the first thing you have to do is either remove the existing focuser body, or if the old focuser was not a FeatherTouch, install the focuser base. One thing to note either way is the orientation of the base plate.
The focuser body is held in place by two setscrews. A common mistake with the FeatherTouch system is to orient the setscrews at the 12 and 6 o'clock positions. This means that you can only turn the setscrews a half turn before having to remove the allen wrench and put it back in 180 degrees and again only have room to make a half turn. Make sure you orient the setscrews at the 3 and 9 o'clock positions and make life easy on yourself (and looking like a pro never hurt either).
Next you put the SIPS in place where the focuser used to be. Tighten the two setscrews in the base.
Finally, put the focuser on top of the SIPS and tighten the three set screws. This makes a nice looking stack. It is a tall stack, so you may need to put the shroud on the truss poles before installing the UTA. Otherwise the shroud may not fit over the unit.
As an aside, I noticed that Starlight started coating the interior of the focuser with flat black, rather than the shiny black anodizing only. Nice touch and great attention to detail.
You unscrew the Lens to collimate the telescope. It takes some effort to unscrew. I doubt it would ever vibrate out on its own; even on a long, bumpy trip. The Lens makes a loud sound like a honking goose as you unscrew it. The UTA makes a nice "drum" to amplify that sound. You should prepare yourself with some snappy comebacks for the comments your fellow astronomers will be directing at you in the dark; you will not go unnoticed.
Next take some Scotch tape (the frosted kind) and place it across the smaller hole in the Positioning Aid. I read that one guy used wax paper and a rubber band, but he may have ran out of tape. I don't see how it could be of any advantage.
Rack the focuser all the way inward and push the Positioning Aid all the way down until it stops. Aim the telescope at the moon, or bright star and spin the SIPS until the object comes to focus. You will instantly know the right spot, there is nothing fidgety about finding it. Spin the locking ring down against the base until tight. Loosen the three setscrews on the SIPS and reorient the focuser angle to a comfortable position (it may very well have ended upside down while spinning the SIPS) . All and all, it was a very easy installation and calibration procedure.
If you installed an entirely new focuser, or flipped the base plate around to place the setscrews in the proper position, this would be a good time to square up the focuser with the Leveling Screws on the base.
The weather the last week or two has been so bad for observing that I was praying even for sucker holes. Night after night it was 95 percent cloud cover, rain, high winds or a combination of all three. Add to that all of the trees in Ann Arbor that further limited my horizon (I sure was not going to drive out anywhere far just to look at clouds). I ended up doing almost all of my observing in pre dawn darkness. This was an instance where it came in handy to have a friend who goes to work at 3am call and wake me if the skies had cleared at all.
You unscrew the SIPS lens, collimate, then screw the lens back in. It is an extra step to remove it, but really it is nothing to worry about. The most inconvenient thing about removing the lens is where to put it while removed. The lenses are mounted very close to the lip of the tube on both sides. If you lay the lens on its side, it wants to roll away. It needs a holder of some sort for safety.
One thing that immediately becomes apparent is that NONE of your eyepieces will come to focus without the lens installed. If you are they type of observer that does not use a Coma Corrector when using higher power eyepieces, get used to always having the SIPS installed.
Using the SIPS with a collection of Ethos and Nagler eyepieces, the scope gave great images all the way to the edge. The field was nicely flat as stars drifted through it (there was no tracking system installed on the scope). I also tried a few cheap eyepieces of various brands to see if they all came to focus, and indeed they did. The cheap eyepieces, even with the SIPS, really remind you why you pay so much money for the good stuff.
About the fifth time I tried to reinsert the lens, it would not seem to thread in. I took a look with my light and saw that the vinyl O-ring had climbed out of its slot, blocking the lens.
I reached up, snatched it, and put it aside for later. The lens silently screwed back into the SIPS and stayed put. I know the instruction manual says "Frequent removal and installation of the lens group is not recommended." , but five times does not seem excessively frequent to me.
It would be easy to press the O-ring (really a "C" ring) back into its groove, but it would be just as easy to use a smaller O-ring at the base of the threads. That would function like a washer so the lens would not unscrew during travel, and remove any noise during installation or removal. I just used the SIPS without a O-ring for the rest of the review, as I was not going to do any traveling with the SIPS installed the scope anyway.
Owners of big Dobs often use binoviewers. On smaller dobs, using a binoviewer often results in a noticeably dimmer image. On larger Dobs (20"+) one would be hard pressed to see any difference.
The SIPS instructions say to remove the lens in order to collimate or binoview, but I could not find a way to get either the Denkmeier or Televue binoviewers to come to focus. They don't work with the SIPS lens in place or removed. Even extending the Denkmeier OCS tube to full length on the Denkmier II binos does not result in a focused image. Using the short nosepiece failed the same way.
This could be a deal breaker if one was a heavy bino use....unless....
Remember earlier when I mentioned that the threads on the setscrews were 6-32 ? That also happens to be the thread size of those computer case thumbscrews that all of the cool kids use to gain quick access to their systems (I know, the really cool kids never install the cover on their cases at all). A bag of four knobs runs $1.00 at the computer store, and are available in chrome, black, and anodized aluminum colors. I chose chrome for the photos.
I replaced the two mounting plate setscrews with the thumbscrews.
I also replaced the three setscrews on the SIPS.
With the setscrews now all replaced by thumbscrews, I was an observing juggernaut. I could change from SIPS viewing to binoviewing in less than 60 seconds. No honking noise and no chance of dropping the SIPS lens onto the primary mirror. I could use high power eyepieces without the SIPS. I could set the SIPS down and not worry it would roll off my stool (the thumbscrews prevented it from rolling). I could now even compare the Paracorr 1 with the SIPS in the exact same scope. It was a liberating experience for a reviewer as anal as I.
First thing I looked at was how well did the Paracorr 1 compare to the SIPS. As expected, the SIPS won hands down. It was not that it had more contrast or light throughput, it was simply a flatter view corrected to the edge. I had several club members ask if the SIPS increased contrast; and the answer is no. I think some have mistaken the slight magnification of the Paracorrs in general as a contrast boost, but four extra pieces of glass in the light path is not going to add contrast. It "tightens up" the view nicely, but don't call it a contrast booster.
Next I wanted to see how well the Denkmeier's OCS compared to the SIPS. Using the OCS in a Dob lets you come to focus without shortening your truss tubes, and it acts a coma corrector. At f/3.3 the OCS holds up better than one would expect, but the SIPS is clearly superior. That difference would not stop me from enjoying the "3D" detailed views of the binoviewers though. I would not be surprised if Denkmeier comes out with a new OCS nosepiece in the near future in order to take advantage of the faster Dobs.
Just for fun, I tried it on my 18" f/4.5 Dob. It normally has a 2" FeatherTouch focuser, but a little configuring and the SIPS allowed focus (with the 1.5" focuser). The correction was there, but so slight that I personally would not spend money on it. YMMV on this, so try a tunable top Paracorr 2 before you buy.
Finally, I compared high power viewing with and without the SIPS. Widefield eyepieces REALLY need the correction offered by the Paracorr family, but as magnification gets higher, you notice less distortion at the edge of the field. Thus, some observers want less glass "in the way" if they don't absolutely need it. I swapped back and forth a few times and decided that I would just leave the SIPS installed. The image simply looked better with no downside that I could detect.
The SIPS package had a few minor teething pains that will probably be ironed out before you even get around to reading this. It is a unique product spawned from two manufacturers that are currently at the top of their game.
If you can afford one of today's uber fast Dobs, you will certainly be in the market for either the SIPS or the tunable top Paracorr 2. The unit that is right for you will depend on your observing habits:
1. If you never binoview, the SIPS is the obvious choice. One time tuning is a nice feature; worth the price of admission alone.
2. If you have some other brand of focuser other than FeatherTouch, and you are not handy enough to upgrade, go with the tunable top Paracorr 2.
3. The tunable top Paracorr 2 is nicely portable between your scopes, but with the addition of a few thumbscrews, the SIPS could be too.
All in all, the SIPS is a great, innovative product worthy of your consideration.
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