Review: Zhumell 2 Inch SEE IT ALL Telescope Filter Set
Posted: 23 February 2014
On many past reports I have noted that I did not have any 2" filters for use with my 2" eyepieces (OPT 50mm and 30mm, Meade 24mm UWA, and Explore Scientific 9mm 100°) and the Tele Vue 2" 2X PowerMate. I do have several 1.25" format filters, including a moon filter. But no 2" moon filter. I finally decided that since I was now using my 2" eyepieces more than my 1.25" eyepieces, it was time to get at least a 2" moon filter. I did some research and first considered an Orion 2" moon filter (13% transmission) for $25. But then I came across the "Zhumell 2 Inch SEE IT ALL Telescope Filter Set" from Telescopes.com, which is a set of 2" filters for $119. The filters are:
Variable Polarizing Filter (transmission 35-40%)
This filter set seemed to be a good selection of filters at a reasonable price. Some research on the set yielded an excellent review by Shekar Govindaswamy at CloudyNights.com. While the filters did not perform in his tests as well as high-end filters (two of which I have in 1.25" format), they seemed to be adequate for my needs. The order was placed on 18 January 2014, shipped on 21 January, and was received on 24 January, followed by an extended period of cloudy skies. I was surprised that the filters were shipped in a thin plastic envelope, with no padding, but they survived. Inside the envelope were the four individually boxed filters:
Bandpass charts were supplied for two of the filters:
Some overlap in the two filters is obvious.
The following usage report is a consolidation of several sessions in the observatory using each of the filters with the 8" LX200-ACF. All of the observations were done from my observatory site (SQM: 21.70 (Magnitude +6.90).
Since my site has minimal light pollution and no streets lights, I used a bright sky from a waxing gibbous moon to simulate "light pollution". Of course, the light from the moon does not match streets lights, but it served a purpose to check on contrast enhancement. I viewed M42 (Great Nebula in Orion) using the 2" 24mm UWA eyepiece (83X). I compared the view with the 2" Sky-Glow filter to the view using a 1.25" Celestron Light Pollution Reduction (LPR) filter on a 1.25" 26mm eyepiece (77X). The LPR filter provided an improved view over no filter due to the increased contrast from darkening the sky background. The stars were sharper, although dimmer and more blue. The 2" Sky-Glow filter provided a very slight increase in contrast over no filter on the 2" eyepiece.
I also did some tests with the moon not in the sky using an object low in my southern sky where a dim grey "light dome" from lights from Tucson and Oro Valley is visible. The view was improved with the filter.
Using the filter on the large faint diffuse nebula IC443 with the 24mm UWA eyepiece + focal reducer provided a good view of the nebula; better than the view without the filter. The view was similar when using the LPR filter on the 1.25" 26mm eyepiece + focal reducer.
Viewed the Flame Nebula and the area of the Horsehead Nebula in Orion with the 2" 24mm UWA eyepiece + focal reducer and 1.25" 26mm eyepiece + focal reducer. The Flame Nebula was nicely visible in both eyepieces when using no filter. Nebulosity around the Horsehead Nebula was visible without any filter in both eyepieces, but the "Horsehead" itself was not detected (I have previously viewed it in the 8" telescope so I know it is possible to see under ideal conditions). Using the 2" Sky-Glow filter, the Flame Nebula was barely visible. The nebulosity at the Horsehead Nebula was faintly visible, but no "Horsehead" was seen. With the LPR filter, the Flame Nebula was faintly visible and the Horsehead nebulosity was visible (but no "Horsehead").
My initial test of the O-III filter was on the large faint diffuse nebula IC443. The nebula was faintly visible using the 24mm UWA eyepiece + focal reducer about 15 minutes before the end of astronomical twilight. I added the 2" O-III filter; there was not much improvement in visibility of the nebula. The view of the nebula was a little better using the 1.25" 26mm eyepiece + focal reducer + Orion 1.25" O-III filter.
I plan to do further testing of the O-III filter on some of the nebulae in Cygnus that can benefit from using an O-III filter.
I initially tested the UHC filter on a night with a bright waxing gibbous moon while viewing M42 (Great Nebula in Orion) with a 2" 24mm UWA eyepiece (83X). I compared the view with the 2" UHC filter to the view using a 1.25" Celestron Light Pollution Reduction (LPR) filter on a 1.25" 26mm eyepiece (77X). The LPR filter provided an improved view due to the increased contrast from darkening the sky background. The stars were sharper, although dimmer and more blue. The 2" UHC filter provided a very slight increase in contrast over no filter on the 2" eyepiece, but M42 was slightly dimmer than with the LPR.
On a dark night I tested the UHC filter on the large faint diffuse nebula IC443. The nebula was barely visible, compared to being faintly visible without the filter using the 24mm UWA eyepiece + focal reducer.
I also viewed the Flame Nebula and the area of the Horsehead Nebula in Orion with the 2" 24mm UWA eyepiece + focal reducer and 1.25" 26mm eyepiece + focal reducer. The Flame Nebula was nicely visible in both eyepieces when using no filter. Nebulosity around the Horsehead Nebula was visible without any filter in both eyepieces, but the "Horsehead" itself was not detected (I have previously viewed it in the 8" telescope so I know it is possible to see under ideal conditions). Using the 2" UHC filter, the Flame Nebula was a nice view. The nebulosity at the Horsehead Nebula was visible, but no "Horsehead". With an Astronomik 1.25" Hydrogen-Beta filter and the 1.25" 26mm eyepiece + focal reducer, the Flame Nebula was nearly invisible, but nebulosity at the Horsehead Nebula was visible (but again, no "Horsehead").
Variable Polarizing Filter (transmission 35-40%)
This Filter is supplied in two cases. You have to open each case and screw in one filter to the other to take advantage of the variable polarizing capability. Each filter seems to have the same transmission value and one filter can be used by itself for minimal dimming.
Here are the filters stacked together:
The transmission amount is varied by rotating the top filter. As seen below, the amount appears to be more than the specification range of 35-40%:
To change the dimming amount after the filters are attached to the eyepiece and the eyepiece is inserted into the telescope eyepiece holder, you have to remove the eyepiece from the holder, rotate the filter, and re-insert the eyepiece back into the holder. That's a bit of a pain. I used to own a 1.25" Meade Variable Polarizer Filter that has a screw on the side of the filter holder to change the dimming amount without needing to remove the eyepiece. That was very convenient. Unfortunately, it was part of my astro gear that was stolen in 2007. A technique that I found effective with the 2" Variable Polarizing filter was to hold the eyepiece in position in the light path from the telescope and look through the eyepiece at the object (out-of-focus, of course) and rotate the filter until the desired transmission amount was obtained.
I first checked the Variable Polarizing filter on Jupiter with a 9mm eyepiece (222X). Using just a single filter, the view of Jupiter was very good. The filter reduced the brightness and glare from the planet, making the cloud bands more easily seen with higher contrast. Using both filters and with the transmission set to maximum, the view of the planet was just slightly dimmer than that of a single filter. However, with transmission set to minimum, the planet was too dim and the view was unusable. I did similar tests with a 24mm eyepiece (83X), with similar results. Using a moon filter on a 1.25" 26mm eyepiece (77X), the view was similar to that with the 24mm + 1 polarizing filter. With a 1.25" 9.7mm eyepiece (206X) + moon filter, the planet was too dim for good viewing. For bright planet viewing with 2" eyepieces, a single filter from the Variable Polarizing filter set is ideal to reduce the glare and make some features more easily seen.
On a waxing gibbous moon, the 2" 24mm eyepiece + 1 filter provided a slightly brighter view to that with a 1.25" 26mm eyepiece + moon filter. Using both filters on the 24mm eyepiece and set to maximum tranmission, the moon was still slightly brighter than with the 26mm + moon filter. With the 2" filters set for minimum transmission, the view of the waxing gibbous moon was too dim to be useful. However, with the tranmission set about halfway, the view was ideal and comfortable.
I also tested the filters on a nearly full moon at both 83X and 222X. A single filter was tolerable but with both eyepieces the moon was still rather bright. With both filters and set to maximum transmission, the view was still rather bright. Minimum transmission was too much and the moon was too dark to view. But at about halfway, both eyepieces provided excellent views of the nearly full moon. Features in brightly illuminated craters were easily viewed.
Using the Variable Polarizing Filter is a much needed accessory for comfortably viewing the moon at its brighter phases. Being able to adjust the amount of dimming for the current phase is a feature that a standard moon filter can not provide.
I checked the fit of all of the filters on my Meade 2" 24mm UWA eyepiece, Explore Scientific 2" 9mm 100° eyepiece, and Tele Vue 2" 2X PowerMate. All five filters would fully screw in on the 9mm eyepiece and PowerMate. However, only the Sky-Glow filter would fully screw in on the 24mm eyepiece; all the others fit fine on the 24mm eyepiece. Apparently, the threads on the filters are not the problem, so hopefully the threads on the 24mm eyepiece will yield a better fit with filter usage. The optical quality of all the Zhumell 2" filters was excellent. Stars were always pinpoints, with no coma or other artifacts at the edges.
As with 2" eyepieces compared to 1.25" eyepieces, using 2" filters vs 1.25" allows more light to reach the eye, generally providing a better view of faint objects. From a dark sky site (like mine), the benefits of the Sky-Glow (and to some extent, the UHC filter) will be of limited value except when viewing objects that appear in "light domes" on the horizon. The O-III filter will be useful when viewing emission nebula and some planetary nebula. I have previously used my 1.25" O-III filter on such objects, so having a 2" O-III filter will provide enhanced views. And as noted, the Variable Polarizing filter will be very beneficial when viewing bright moon phases, acting as a "moon filter" with my 2" eyepieces.
The Zhumell 2 Inch SEE IT ALL Telescope Filter Set is an excellent value that can provide filters that satisfy many needs. Yes, there are higher quality (at higher costs) filters available and those filters can be worth the money to some observers. However, if you want to save some money and still get good views, the Zhumell 2 Inch SEE IT ALL Telescope Filter Set can be a worthwhile addition to your accessories.
I will provide updates on using these filters on future Cassiopeia Observatory Reports.
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