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Jul 17, 2017 Filter driers are typically shaped like a hot dog and are about the same diameter. If one end of the filter drier is a markedly higher or lower temperature than the other end, it is likely that the liquid line filter drier is clogged and may need to be replaced in order for the unit to work properly again.
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Founded in 1998, DGM Optics, has been offering ultra-high quality Off-Axis Newtonian Telescopes, and highly regarded Nebula Filters such as the NPB for amateur astronomers worldwide. The highly sought after DGM Optics Nebula Filters are the culmination of my 25+ years as an expert in the field of Optical Thin Films combined with my love of astronomy since 1966 when a cheap 60mm refractor showed me the rings of Saturn and craters of the Moon, hooking me forever!
My keen knowledge of Optical Thin processes and designs allowed the development of astronomy filters from a standpoint that most astro-filter makers did not enjoy, in that I was able try many different design approaches. And as such I had no preconceived ideas about what constitutes a good vs. lesser LPR/Nebula filter design. And so after “auditioning” 20-25 different designs from 1993-1994 I settled on the first two filters in the DGM arsenal, the NPB and VHT. Now for various reasons both designs sat on the shelf until around 2001 when I finally found a company to do the first production run in 2002.
The next problem was that while I knew both were very good filters, very few in the wide world of amateur astronomers knew the same. So in 2005 renown astro-gear author Phil Harrington(Star Wares) who had viewed with both filters previously, offered to include both filters in the August 2005 Astronomy Magazine article “Secret Weapons”. And while the VHT did well, the real star of the show was the NPB which as a “UHC-type filter” was rated as the top filter in that category vs. nine other top quality competitors. This was a sentiment that was also echoed by well respected amateur filter performance guru David Knisely in his 2006 review on the very popular CloudyNights website.
Next in 2007 came both the GCE and the OIII to round out the DGM Optics filter offerings. And the rest is history where currently DGM Optics Astro-Filters are recognized as some the best performing filters you can get.
The Filters
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The NPB
The NPB is the ONE filter to have if you have just one, and now regarded as the top narrowband (UHC type) filter in the world. Judged by renown astro-equipment author Phil Harrington as the best of nine leading competitors in the Astronomy Magazine review 'Secret Weapons' (August 2005). With the NPB more objects show enhancement, than any other filter in it`s class, and is also a useful Imaging filter. Visually bright nebula seem to be 'switched on' with this top shelf filter designed by Dan McShane, Optical Thin Film expert and founder of DGM Optics. One observer described the NPB as a 'UHC on steroids'! And, with ultra durable Ion Assisted Plasma Coating Technology used to produce your NPB Filter, it will provide decades of flawless performance.
The VHT
The VHT is a 'mid-band' Nebula/LPR filter that is the perfect match for smaller scopes, or binoculars that can use filters. This filter provides a good balance between the NPB and GCE with regards to contrast vs. field background and star brightness. In addition to the VHT`s excellent visual performance it is also a very good astro-imaging filter with high H-Alpha transmission, and transmission exceeding 90% from 486.1 to 501nm, which includes H-Beta and both Oxygen lines. As with all DGM filters, the durable Ion Assisted Plasma Coating Technology used to produce your filter ensures decades of high quality performance.
The OIII
The DGM Optics HPOIII is your perfect compliment to the NPB when you need a more aggressive Nebula filter that really shines with larger scopes. This filter has a bandwidth of approx. 15nm for those faint, elusive objects, but also has a feature that most other OIII filters don`t with high transmission at H-Alpha. For a visual OIII filter this is important as it provides a bit more 'optical throughput' than leading competitors. As with all DGM Optics filters durable Ion Assisted Plasma Coating Technology ensures an ultra-hard, low scatter coating.
The GCE
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The GCE takes a different approach to Wideband LPR filters by employing a 'Notch' design which excludes all the bad stuff, from 540 - 590 nm, while allowing the rest of the visible spectrum to transmit over 90%. This results in a 'wideband filter' that provides a slightly brighter image than traditional single band filters which reject most red light. The GCE excels as a general contrast booster with an absolute minimum of star dimming, and really enhances dark material in the Milky Way, and even adds some degree of improvement for galaxies. They are also an excellent match for binoculars and the low power-per-inch they offer. And as with all DGM Optics filters features super durable Ion Assisted Plasma Coating Technology.
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