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Denkmeier Filter Switch

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Denkmeier Filter Switch
Denkmeier Filter Switch

Ok, I admit it. I'm one of the laziest people I know, especially when it comes to astronomy. I don't like doing "work" and prefer to use my star time efficiently observing or imaging, not "working". I eliminate as much Ôwork' as possible.

One of the best "time savers" was the purchase of my Denkmeier R1 Power X Switch diagonal. This has a built in barlow and reducer that allows three magnifications for the price of one eyepiece (or two if using a binoviewer) and no fumbling of equipment or teardown of the optical train to change anything. Just "switch" the lenses via two arms inside the diagonal. I've done an earlier review on the Denkmeier PxS diagonal but it is the basis of their latest innovation, the filter switch. The filter switch works similarly to the Power Switch and is available on any setup (newt, refractor, SCT etc) that can use a Power Switch.

The photo above shows the R1 diagonal, filter switch, Power X Switch and binoviewers.The two thumb slides on the filter switch move 2" or 1.25" filters in and out of the optical train. The two arms on the Power switch move a barlow or reducer into the optical train.

The one snag with any optical system is filter usage. It is simply a pain if you want to swap filters. Observing grinds to a halt. You have to pull the diagonal with one hand, use a second hand to unscrew the filter, put it in the case and use a third hand to get the next filter and screw it into the diagonal. Then you have to put the whole mess back in the scope and hope the target is still in view after pulling the diagonal. If you have a DSO filter on the diagonal you are most assured that your next target will probably be a galaxy where you want to remove it. As soon as you get that done, dollars to donuts then somebody will want to see a nebula again. Back on with the filter. If you're doing planetary work with filters, juggling five filters in five minutes is par for the course. Filter switching on an eyepiece is marginally easier but there is still a lot of juggling.

Like I say, I'm lazy and hate all the juggling. I scanned far and wide for an easier way of managing filters. I had a three place filter wheel for a while. It was a pain to rotate and even a pain to change the two 1.25" filters it allowed. I next tried a Sirius VFS (Variable Filter System) which is like a continuous spectrum filter. It was interesting but useful only for planetary observing. Switching to DSO's involved the familiar juggling act. When I switched to a binoviewer I just didn't feel comfortable hanging $1300 bucks on the VFS's plastic housing and set screw. So that meant a 2" diagonal and good-bye to 1.25" format filters and the VFS.

I resigned myself to buying more expensive 2" filters and more juggling. I looked into the 2" filter slide Lumicon has, but even if it could be adapted to the PxS diagonal, the filters are still exposed to the elements and unprotected. I even looked at a 2" filter wheel from England. Big $$$.

Then I heard about the Denkmeier Filter Switch. Basically it's the same concept as the PxS lens switch except with filters. I sent my R1 switch diagonal in for the modification that handles both 1.25" and 2" formats.

It's almost anticlimactic because there isn't "much to say" about the filter switch. It is simple in concept, simple to use and yet works flawlessly. The fit and finish is as precise as you would expect from a Denkmeier product. Like the lens switch, the filter switch is two plates in the optical train where two filter carriers slide in from each side. The carriers are square plastic and have a round 2" hole for the filters and a small screw to hold them in place. When inserted in the switch body, two thumb lobes protrude from the near side and applying pressure slides the filter carriers easily into or out of the optical train. The filter switch allows one filter, no filter or the other filter. The filter carriers are easily removable by simply sliding them all the way out. I only have the two carriers right now but can see a day where all my filters, both 2" and 1.25" will be in carriers. For 1.25" filters there is a Ôstep down' donut that then fits in the 2" carrier hole. Again the filters are held in place by a small allen screw.

The photo above shows the filter switch with the Power X Switch and binoviewers removed. I'm holding a carrier with a 1.25" stepdown. The other carrier is in the left side of the filter switch and the "thumb slide" is protruding from the backside.

In operation the filter switch works flawlessly. The carriers are precisely fitted so that they are snug enough to keep contaminants out of the switch but still allow easy, one finger movement into or out of the optical train. The carriers are also snug enough that they don't Ôslide' with odd diagonal angles. In the dark, finding the filter slide thumb lobe was easy and the feel positive. From a usage standpoint all I can compare it to is like going to an eye doctor for a test when they do the, "Which view looks better, number 1 or number 2? Now which looks better, number 2 or number 3?" That's what it's like using the filter switch. Effortlessly checking out different views and finding what is best.

Currently I only have two carriers and 6 1.25" step downs. Needless to say the purchase of additional carriers and step downs would be highly recommended at the time of purchase.

At the star party Driftless Zone star party I had the filter switch loaded up with my 2" Astronomik CLS and UHC filters, one is broadband and the other narrow. Talk about being able to hit every DSO target in the sky from planetaries to galaxies and never having to touch the optical train except for viewing through it! Imagine different magnifications and filters available with just a flick of a switch and some focusing. Needless to say I wandered all over the sky from M42 to NGC2903 to M3 at a whim without having to Ôclassify' and Ôorder' my targets according to the filter screwed into the diagonal.

At the summer WOW Star Party planets were the priority. Again the filter switch was a wonderful addition to the evenings but I could only have 6 1.25" filters ready to go but had to swap them in and out of the two carriers. That's when I decided I saw additional carriers in my future.

At NSP I did both planetary and DSO observing and used the filter switch extensively without a problem. I've used the filter switch for about four months now and feel it was as smart an investment as the original R1 diagonal.

On the "pros" side the filter switch has many. One side benefit is that I will be able to Ôdownsize' my existing 2" format filters to 1.25" filters and still use the binoviewer. The only reason I purchased 2" filters in the first place was for use with the diagonal. A 2" filter is cheaper and less of a problem than buying two 1.25" filters for each eyepiece. There are also potential optical issues when using two separate filters on a binoviewer. With the filter switch I will be able to keep my binoviewers in a sturdy 2" diagonal and optical train, yet be able to run single 1.25" filters. This Ôdownsizing' alone to 1.25' filters will definitely save money in the long run and make the filter switch pay for itself.

Another advantage to the filter switch is Ôpositive filter control'. Usually by the end of the night I have my filters laying all over the place getting dewed up or in a pocket picking up who knows what. Some nights I've spent considerable time just trying to remember where I set one down. Since the optical train does not need to be broken down, even changing carriers is a simple one handed operation, the filter carrier comes out, goes in the case and the next one goes in. On the nights when I'm doing strictly DSO's I often have no need to swap filters at all since the CLS and UHC are ready to go anytime they are needed.

A subtle advantage is that there is no weight change in the optical train. Often when pulling the diagonal to swap filters the scope would Ôdrift' some in declination due to the weight imbalance or me pushing the diagonal back in and I would have to reacquire the target.

Along these lines is the advantage of never having to Ôretighten' setscrews holding the diagonal. If you are running a heavy optical train like I am, with a binoviewer and heavy eyepieces you want to make sure the setscrews are tight. Having the filter switch and no need to pull the diagonal for a filter change drastically cuts down on the setscrew fumbling. This not only cuts down on the marring on the diagonal barrel but also lessens the risk of leaving one of the setscrews loose and losing the diagonal.

About the only "con" I can think of is that with the filter switch is that it is not possible to directly stack filters. I rarely do this except for possibly stacking a ND filter and color filter on the Moon. If I feel I absolutely have to stack filters I could still do it on the eyepiece(s).

The filter switches are available as an option on the Power x Switch setups. If you can run a Power Switch you can also run a filter switch. The modifications can also be performed on regular William Optics diagonals. Additional carriers will absolutely be a "must" for those that use filters extensively.

Once again it looks like Denkmeier has come up with a winner that blends simplicity, quality and common sense into a winning product.


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