Amateur Astronomy Filters

Eyepiece filters usually screw into the bottom of the eyepiece and come in sizes that fit both 1.25 inch and 2 inch eyepieces. These filters can enhance the contrast of low surface brightness objects like diffuse nebula. They can be used to en- hance the surface features of the planets and Moon, reduce glare of very bright A N T E L O P E V A L L E Y objects, and even enhance the definition of images. There are filters that reduce ASTRONOMY CLUB, INC. the effects of light pollution and those that allow the spectrum to pass through at A 501 (c)(3) Non-Profit only one frequency. Several are summarized below. Organization

Solar Filter: This is the filter that will allow you to safely observe the closest star On the web at: to the Earth - the Sun. These filters fit snugly over the front of the telescope and www.avastronomyclub.org are made out of either coated glass, or a Mylar material.

Blue Filter: A Wratten #44A, 47B or 80A is used to detect high altitude clouds on Mars, white ovals and spots in the belts of Jupiter, and the zones of the clouds of Saturn, and to reduce the glare of the bright Moon. The 80A is the filter to have if Tel: (661) 724-1623

you only buy one filter. VALLEY ANTELOPE Or (661) 822-4580 Green Filter: A Wratten #58 allows you to see more clearly the edges of the

Martian polar caps and enhances the belts and the Great Red Spot in the clouds INC. CLUB, ASTRONOMY of Jupiter.

Yellow Filter: A Wratten #8, 12, or 15 can improve the markings in the clouds of Venus and enhance dust storms on Mars.

Orange Filter: A Wratten #21 is one of the most useful filters. It brings out details on Mars and enhances some zonal details on Jupiter, also darkens the blue sky so daytime observations of Jupiter, Venus and the Moon are much improved.

Red Filter: A Wratten #23A, 25, or 25A are used to enhance contrast on Mars, Jupiter, and Saturn. A red filter, however, is fairly dark, so it works best on larger aperture telescopes that give brighter images. Switching between red and blue filters can sometimes bring out subtle coloration on the surface of the Moon.

Polarizing Filter: Cuts down the glare when observing a nearly full Moon, making it easier to see ray structure. It will also cut down daytime glare. A “variable” Moon filter will allow you to dial in a specific amount of neutral density light reduction. For terrestrial photography with your telescope, this filter will reduce sky glare early in the morning and the late afternoon.

O-III Filter: A bandpass filter used to enhance the contrast of diffuse nebula by allowing the doubly ionized oxygen band through. Great for the Ring Nebula, M57, crucial for the Veil Nebula, and the North American Nebula.

Ultra-High Contrast Filter: A UHC bandpass filter is used to enhance the contrast of diffuse nebula. Allows the O-III light through and Hydrogen Beta. Great for the Swan Nebula.

Light Pollution Filter: LPR filters are designed to darken the background sky by blocking mercury vapor light transmission and enhancing transmission in the hydrogen beta, doubly ionized oxygen (OIII) and hydrogen alpha regions of the spectrum. The filter increases the contrast of deep-sky objects, emission nebulae in particular, with the background light-polluted sky.

Hydrogen Beta Filter: The only way to see the Horsehead Nebula and the California Nebula. This filter is highly specialized.

Hydrogen Alpha Filter: These expensive filters are essential if you want to observe and photograph solar prominences. This spe- cial filter transmits a very narrow slice of the spectrum, typically 1/5000 to 1/3000 of the visible spectrum's full width. The trans- mission window of these ultra-narrowband filters is generally centered on the bright hydrogen-alpha (H-alpha) line at a wave- length of 656.3 nanometers (6563 angstroms) in the red. Phone: (661) 724-1623 or (661) 822-4580 E-mail: [email protected]

Antelope Valley Astronomy Club, Inc. P.O. Box 8545 Horsehead Nebulae Lancaster, CA 93539 M57 – Ring Nebula We’re on the web! http://www.avastronomyclub.org

You Are Invited to Join the Antelope Valley Astronomy Club!

A 501 (c)(3) Non-Profit Organization Monthly Meetings and Activities AVAC Membership Application The AVAC holds monthly meetings the second Friday of every month at the SAGE Planetarium, 38060 20th AVAC Offers A Variety Of Membership Options: Street East,(located on the northeast corner of East Avenue R and 20thEast) at 7:00 PM. The meetings Family Membership Cost (See Below) include guest speakers and monthly programs about Individual Membership the fascinating night sky, while giving members and guests a chance to get together to talk about the stars Junior Membership (13 and younger) Total______or other topics of interest. We hold monthly public star parties and frequent ‘deep sky’ observing sessions as Dues are prorated each month. See table below Example: A Family Membership paid in June is $17.50 weather permits. We offer our members resources to help you learn more about astronomy including Membership Dues classes, telescopes and books. Month Family Individual Junior JAN $ 30.00 $ 25.00 $ 15.00 FEB $ 27.50 $ 22.92 $ 13.75

Directions to the Meeting MAR $ 25.00 $ 20.83 $ 12.50 APR $ 22.50 $ 18.75 $ 11.25 MAY $ 20.00 $ 16.67 $ 10.00 JUN $ 17.50 $ 14.58 $ 8.75 JUL $ 15.00 $ 12.50 $ 7.50 AUG $ 12.50 $ 10.42 $ 6.25 SEP $ 10.00 $ 8.33 $ 5.00 OCT $ 7.50 $ 6.25 $ 3.75 NOV $ 5.00 $ 4.17 $ 2.50 DEC $ 2.50 $ 2.08 $ 1.25

Checks should be made out to ‘AVAC’ You may mail them to the Club PO Box or bring checks or cash to the meeting. Do not mail cash. You may also pay via PayPal on our website.

Name(s)

Address

Phone e-mail

A N T E L O P E V A L L E Y A S T R O N O M Y C L U B, I N C.

P.O. BOX 8545 Lancaster, CA 93539

Phone: 661-724-1623 or 661-822-4580 Email: [email protected]